FetLife profiles and TSR
TSR finds FetLife profiles using the profile's nickname. This is the name displayed at the top of the profile page. For example, 123-456-781 on this profile. When you use the "Find on FetLife" button on TSR, the Slave Registration Number is looked for as the exact nickname. If the nickname has extra characters, then this won't work. So nicknames like SLRN-123-456-781 or 123-456-781-alice won't work.
TSR does this so there can only one unique profile corresponding to each Slave Registration Number. Otherwise Alice could create 123-456-781-alice and Bob could create 123-456-781-bob, and we wouldn't be able to tell which one is the real 123-456-781.
If you already use FetLife, you can either create a new profile with your number as its nickname, or change the nickname of your existing profile. There's a "Change nickname" tab on the "Edit profile" section of FetLife.
If you are registering from July 2016 onwards, the registration page recommends that you maintain a profile with your number as the nickname: either a new profile or by changing the nickname of your existing profile.
People increasingly expect to be able to find people by Slave Registration Number using the "Search for ..." box at the top right of any page of FetLife.
If you need to create a new profile on FetLife, you will need to use an email address that is not currently used by another FetLife profile. Email accounts from free providers like Gmail.com etc are ok. In fact, with Gmail, if you were already email@example.com, you could use the address firstname.lastname@example.org and still receive the emails sent there. Some other providers have similar options for adding secondary or alias addresses without creating a new account.
Once you have your FetLife profile set up with the number as the nickname, you can use all of the FetLife profile features to upload pictures of barcode tags or tattoos, "mugshots", descriptions of your status and relationships, etc as you wish or as your owner requires. You can also use FetLife's relationship links to link your number's profile to your owner's profile and state the form of your relationship. All this is documented in FetLife's help pages.
And if you've not already done so, please come and join us in The Slave Register group on FetLife.