Register On-Line through the USMS Web site at,

http://www.usms.org/reg/ 

This site lets you register for both USMS and Arkansas Masters.  If your zip code does not put you in the Arkansas LMSC area you can still register with Arkansas Masters by clicking on the -   If this is not your region, click here to start over - link and then clicking on the state of Arkansas in the map that appears. The club ID for Arkansas Masters is - ARKM

Or you can download a Registration form to mail in.

USMS and Arkansas Masters Swimming Registration Form