It's only required to connect Dev board to the PC using a USB Micro B cable, which usually comes along with it. You can therefore go to step 2. Nevertheless, if you are using an AI-Thinker’s ESP32-CAM, you need to keep reading step 1.
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Given the fact that the ESP32-CAM lacks any kind of USB connection, in order to flash the firmware we ought to use a USB to serial TTL converter. This converter might be only a cable or a chip (just like those of the following picture) however, both of them accomplish the same purpose — the only thing that matters is recognizing the TX and RX connections.
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In case you are using a converter like the one on the left of the picture, each pin is labeled with its function. On the other hand, if you are using a converter like the one on the right, the cable colors will tell you its function.

If you are using a converter like the one on the left, please connect the TX pin from the converter to the RX pin of the ESP32-CAM. Conversely, connect the RX pin from the converter to the TX pin of the ESP32-CAM, then proceed to connect the ground terminal from the converter to the ground terminal of the ESP32-CAM.

You’ll notice that the ESP32 has two different Voltage input terminals, one for 5 V and the other for 3.3 V. It’s up to you and your resources to decide which power terminal to use, however please be quite aware because connecting 5 V to the 3.3 V terminal will damage the chip.

Some USB to TTL converters have a little jumper which allows you to select its output voltage, set it either to 3.3 V or 5 V and proceed to connect the converter’s Vcc pin to the corresponding ESP32 pin according to the voltage selected by the jumper. The following image shows you how to connect the ESP32-CAM using the 3.3 V input. Finally, the converter is connected to the PC’s USB port by using the cable that comes along with its purchase.

If you are using a USB to TTL converter like the one on the right side of the first picture (the one that looks like a cable) you won’t have the chance to select the voltage. Instead, it has 5 Volts output (red wire) which you should connect to the 5 Volts input pin of the ESP32-CAM (this pin is actually on the opposite side of the 3.3 V input) The following picture shows the appropriate connection when using the 3.3 V power input.

Also, notice the fact that we have connected the “IO0” pin of the ESP32-CAM to its ground terminal. That is because, in order to set it into flash mode, we need to short out that pin.

There are plenty of ways to flash Tasmota firmware to our device, but we’ll see one of the easiest in this guide since it requires no installation of any kind of tool. Let’s head to the Tasmota flash web tool.

The page should look like the one above, There you can select Tasmota firmware version that you wish to install. If you are using a device other than the ESP32-CAM, you can choose the option “Tasmota (english)”(which is usually selected by default) and then hit the “CONNECT” button. However, if you are using the ESP32-CAM, you must specifically choose the firmware for this device. The following GIF shows the whole process using ESP32-CAM. The process is the same for all devices, you only need to select the appropriate firmware version.

A pop-up will let you know that the installation was completed. If you are using ESP32-CAM, do not click the “NEXT” button or you won’t be able to set up the wireless connection for the device, instead, please remove the wire shorting the “IO0” pin to “GND” and now you can click the “NEXT” button to move to the next step. If you are using any other chip than the ESP32-CAM, just click on the “NEXT” button to continue to the next step.

Now we are going to select the WiFi network to which our newly flashed Tasmota device will connect to.

After selecting the WiFi network, a new window pop up displaying the message “VISIT DEVICE”, click on it to go to the Tasmota dashboard.

Given the fact that Tasmota is a firmware built for a variety of different devices, we need to tell Tasmota which device we are using. In order to do so, while on the Tasmota dashboard, let’s head to the “Configuration” section, then look for “Configure Module” and then select the appropriate device from the dropdown menu. First, I will show you how to configure the ESP32-CAM, so in this case the appropriate device is “ESP32-Cam(2)”. The following GIF shows you how to configure the ESP32-CAM.

If you are using a chip other than the ESP32-CAM variant, you must select “ESP32-DevKit(0)”. If you are using an ESP8266, you must choose “Generic(0)”.

Taking into account that most of the ESP based devices come with a built in LED, we can use this to test if the installation was successful. Go back to Tasmota’s dashboard main menu and look for the “Toggle” option, this will make your board’s LED turn on and let us know that the installation went well.