How to add players who don't use Meeplay to a game
Add someone who played with you to a game even if they don't have the app: create them as a player with their name or count them as an anonymous player.
To log a game, not everyone needs an account. You can create a player with that person's name (it stays saved for next time) or, if it doesn't matter who it was, count them as an anonymous player.
Have the Meeplay app installed and be logged in to your account.