Edgetx has its own companion software. There are some stylistic differences between opentx and edgetx (things will look a little different on the screen), but tutorials for opentx should teach you the basics that you need. Start with an easy 3 or 4 channel plane. Remember that you don't NEED to do everything at once - simply figure out how to bind and get the control surfaces moving on the plane (in the right directions with reversing). From there Figure out how to add rates to a switch, then make a kill switch for throttle, add a picture icon for your model, add modes (if you have a stabilizer), then add voice prompts to tell you what the switch you just flipped should be doing. I have my radio announce things like Armed (engine on), Engine off, high rates, medium rates, low rates, flaps on, flaps off, stabilized mode, and acro mode... having the voice tell me what switch I just flipped while I'm trying to watch my plane in the air was a real benefit to me when I first set it up.
Start slow - you definitely don't NEED to figure it out all at once. Just solve one problem at a time, and after a bit you'll have a very customized transmitter that does exactly what you want it to. If you run into a specific roadblock, google it or ask here and we'll do our best to help.
Then when you want to add a second plane - just copy your first model (where you set everything up), rename it, change the picture and bind it with a different receiver number or different protocol.
And back things up in the EdgeTX companion often so you can go back a few steps if you mess something up.