If you have followed the previous 2 tutorials for setting up a User Account and Adding a boat then you should have a simple boat profile page where you are assigned as the only crew-member as "Captain and Owner".  You can invite other users to be assigned as crew-members for your boat as follows:

1. On your Boat Profile page click on the "+" symbol to the left of the "Crew" heading. 
2. Enter the email of the person you would like to invite and enter their "role" on the boat.  If you want to give that person rights to edit, add and delete content on the boat profile page then click the checkbox labelled "Is admin", otherwise uncheck the box to give the crew "view-only" rights. 
   
   1. For example, in a husband and wife 2-handed crew then the husband may have set up the boat and be assigned the "Captain and Owner" then the husband would enter his wife's email address here and assign her role as "Admiral" and leave "Is admin" checked.  Or vice-versa if the wife is the owner.
   2. Other roles may be "Ships wife" (with "Is admin" checked) for a shore-based individual who has rights to post and edit content on the page on the owner's behalf.  Similarly you could have many crew on a larger boat with various roles but who are not admins of the page (Uncheck "is admin").
3. Once you have entered the details above then an email will be sent to the crew-members email address which you entered inviting them to join the boat.  Instruction are in the email.  They will be directed to set up a User Account as outlined in the tutorial "Set up a User Account".  It is important that they MUST create their User Account with the same email address as the invitation was sent to.
4. Once they have logged in they should see the invitation appear under the heading "Invitations" on their User Profile page with the buttons "Accept" and "Decline" next to it.  Once they click "Accept" their User Profile will be linked to the Boat Profile and their name will appear under the "Crew" heading for the boat.