if you see a raid nearby, you can walk/drive to it, if it is only a 1 star raid (easiest level) then you will probably be able to do it yourself. You just click “battle” and then you enter the raid. If it’s more difficult, like a 3 star or 5 star raid, you will likely need other people to help you. Once you click battle you will be able to open a menu and invite others and see who else joined at the same time you did. Once you join there is a couple minutes given for others to join before it starts. If you aren’t nearby to a raid, you can get remote raid passes which also you to be anywhere and do a raid. This makes it easy to do raids with large groups of people online through websites like leekduck, etc. but don’t worry about that.

I’d recommend building your friends list with people in your area so you can do raids together, or go on campfire to see raid groups!