Don't try to start with a web app. I'd recommend looking into Fable (the F# to js compiler). Write f# and run it in the browser, I found it to be a better and faster feedback loop when compared to a .net project.
Play around with the f# language (don't touch the js inter-op) until you can figure out if you actually like f#. Take it slow, it's not just a new language, it's a different paradigm. If you get frustrated, take a break for a few days, watch some f# videos and let the knowledge settle. You'll eventually start having evrika moments.
Look into other functional languages. Maybe you'll like others more. Accumulate knowledge and experience until you start thinking "I could do this a lot simpler in f# (or other lang)".
Then, if you want to use f# in a c# project you just need to learn how to reference a project in another project.
If you want some resources:
https://fsharpforfunandprofit.com/video/ some of these videos can get you "hyped up" for functional languages
https://www.youtube.com/watch?v=4YO4XmtPFQw
https://www.youtube.com/watch?v=EPfpO_6uFAA
the entire https://fsharpforfunandprofit.com/ site is a good resource to learn everything from the basics to the wizard level stuff.
As an editor you can use Visual Studio but I'd recommend Visual Studio Code with the Ionide extension.
