It's a little bit more straightforward to add a player on the ROBLOX Player. At the top of the home screen, you'll see "Friends" and then a circle, that has an icon of two players, saying Add Friends.

Select the Add Friend option as it appears on the profile page. It’s recommended by ROBLOX to send a polite message informing them of who you are and which game you met in, for example, “Hi ...