How do you add friends on LoL?

To add friends on League of Legends, open the client and click on the "Friends" tab. Then, click the "Add Friend" button and enter your friend's summoner name or their Riot ID. Once you send the request, they will need to accept it for you to become friends in-game. You can also add friends directly from in-game by clicking on their name in the scoreboard and selecting the option to add them.