If you haven’t done so already, you will need to register to vote (generally) 30 days before the general election on Nov 4.
Only two states, that I am aware of - Washington and Arizona - offer online registration (this absolutely dumbfounds me). Links for those two can be found here:
Otherwise, you can go here: https://ssl.capwiz.com/congressorg/e4/nvra/
Select your state, fill out the form, print and sign it and mail it in.
This takes very little time but is hugely important.
If you’ll be at least 18 come election day and you don’t vote, you don’t have the right to bitch about who wins or loses.
Get to it!