Now that you are here you have learned a lot of things, but there a lot of things to learn. A good way to learn it is to play CTF and after the contest look up for the write up and try to understand the solution.
You can go to CTFTime and see the CTF schedule and join or create a team, We'll share the link to the calendar: upcoming
If you want to keep playing you can go to OverTheWire and try to solve the levels in this room:
Now let's get to web app hacking!