To Join the Crew ...  Submit your Xbox gamertag AND your Rockstar social club name

​IMPORTANT:  CREW MEMBERS - Please have your gamertag linked to your Rockstar Social Club Profile 
and set visibility settings  to either "Friends & Crews" or to "Everyone"  
Here is a tutorial video showing how to do this:  https://www.youtube.com/watch?v=7OsYa9SzsiY