As someone who builds computers, repairs phones and tablets, and is the go to tech support guy for just about everyone I know...
Don’t bother. I love my Firestick. It’s great for watching videos and listening to music. That being said, it is not meant for web surfing or even playing games. Both are possible on the Firestick, but neither is going to work well. I have tried installing every porn streaming app I could find on mine, and none of them work.
There is an alternative, if you’re willing to put some initial effort in. You can stream porn from your Android phone or tablet to your Firestick fairly easily. You’ll have to set the FS up on the same network and possibly download an app to make it happen, but it is doable. Btw, don’t bother trying it with an IPhone or IPad. Apple doesn’t play well with others, despite recently relaxing restrictions. You may be able to get it to work, but it most likely won’t work well.
Personally, I have both a Firestick and a basic Chromecast. I use both as they were intended, the Firestick is for directly streaming video and music while the Chromecast is my go to for casting porn. Seriously, the only time the Chromecast gets used is when I/We are wanting to watch people doing adult things. Then again, I also have a low end Android tablet which is only used for casting said adult content to the television.