Accepting an Invitation to Collaborate

If you receive an invitation to edit someone's book, it will come in an email and look something like this (only the text will hopefully be intelligible):

Basically, it says you'be been invited to collaborate on a book and invites you to click the link. You click on the blue link as directed and it will take you to the mixbook site and ask you to sign in (unless you are like me, and are always signed in...):

Once you are signed in, you will get a screen that looks like this:

You can choose to accept, or ignore the request.

Once you click accept:

Congratulations!  You are now a contributing member of this book!