By ticking « I agree », you accept the terms of use and the way the app uses your information. Before you tick, find the optional boxes.
Read each box separately.
Tick the required box (the terms of use).
Leave the advertising boxes and the sharing-with-« partners » boxes empty. You should be able to continue anyway.
If you cannot continue: the app requires that sharing. Read its privacy policy to find out who your information is shared with, then decide whether the app is worth it.
Limitation: you can change your mind later, in the app’s privacy settings.
To picture it: ticking « I agree » is signing a promise. Better to know what you are promising.