If you're a membership-based organization, you'll need to set up at least one membership level via the manage Memberships admin screen (accessible by going to your Magnet admin menu at the left end of your menu bar.)

The following Magnet.Help article will walk you through the different membership options you have available under this admin screen and how to use them:

http://www.support.omnimagnet.com/magnet.help.html?resource=165&article=true

Remember that the Membership Level # that is associated with each membership level is the number/value that you're going to use in Column L of your MUUT file when submitting your user/member information. Without this, we won't know what membership level a given member in your organization is.