STS Module activation problems

[Murrini]

I am just starting out with both osCommerce and the STS add-ons. I have fresh installs of both (osCommerce is version 2.2RC1 and STSv4.5.8) and have followed all install instructions very carefully but... When I go into the admin panel to modules and click on the STS module it shows the options for payments. I have refreshed the screen and tried accessing it from another computer. In my file manager it shows all of the appropriate files in the includes\modules\sts and \sts_inc files. What am I doing wrong?!