Unfortunately you cannot merge. Google services will have an option to switch between the different accounts. The priority order is shared, and to change the order you have to log out of all your accounts and log in again, with the primary account first. I decided to keep my @gmail.com account first, so I only have to switch to the @example.com account when I check GMail.
Could be much better, of course. I was personally a bit frustrated with the process.
