After logging into the app for the first time you will need to complete your profile.
Simply follow each step. Your profile is complete when you have all green ticks ✅.
However if you are unable to save any information - i.e. the app will not allow you to select SAVE - it will be because information is missing from the section you are working on. EVERY field with a * must be completed in order to save your profile and move on to the next step. Common things that get overlooked are:
Correct country code for telephone number