Hi and welcome STS!!
To be able to download mods here you need to make a donation.
http://www.subsim.com/radioroom/payments.php
Select the 5$ option and you'll be able to download up to 25 mods daily.
It's a way to help out the community
You can find more info here
http://www.subsim.com/radioroom/showthread.php?t=203091