Registration
Registration is necessary to take advantage of all FrozenSoul features Part of this process involves associating your Enjin account with your Minecraft account ("syncing")
Overview
Enjin is a gaming network which provides FrozenSoul with much of its front-end structure including the forums and the reward store. In order to take advantage of many of the in-game conveniences FrozenSoul provides, you must register an Enjin account and then associate your Minecraft account(s) with your Enjin account. This is known in the community as "syncing."
Partway through the process you will be asked to join a vanilla server to verify the connection, so you will need to be prepared to do so. The version will be the latest minecraft release and can be found as an option on some launchers or by simply using the Mojang launcher. Upon joining the vanilla server you will be given a code to input into the FrozenSoul website when prompted, finalizing the process.
The above is a very brief outline of the steps involved. If you're having trouble you can see the wiki guide here or the help section's original syncing guide here.