OK so it's probably a good idea to apply for your DMR ID soonish since it may take a few days. Even though you have a call sign, that's not what is used for message routing on the DMR network. Instead, a unique identifier, granted by a central authority, lets you identify who is calling and who you want to call. It's a little like a phone number!
Visit http://dmr-marc.net/ to apply for your ID. You'll likely want one for each of your DMR radios
Click on Contact Us
Then select I'd like a USER ID for my radio
You'll get this lovely warning:
Click on User Registration and enter in your amateur radio call sign
Fill out the rest of the form
When complete, click Register and you'll get a notice that registration completed
A few days later (please be patient with the people running the registration, they're volunteers!) you'll get an email with your DMR ID
Note that your name, call sign and ID number are not private - they are visible in the DMR user database registry!