To create a new thread, press the orange button (Post new thread) which can be easily seen here (Alliance of Valiant Arms (AVA) Hacks & Cheats - MPGH - MultiPlayer Game Hacking & Cheats - Hacks, Cheats, Downloads, Trainers, Games)
To add a virus scan, go to the following sites:
Jotti's malware scan
After that, upload your file by clicking the browse (or choose file) button then click on submit (or scan it!) Then copy the URL from your navigation toolbar of the browser you are using (eg: Google)
To add an attachments, click on the orange Post new thread button, scroll down then click on Manage Attachments.
Press Add file on the upper top right corner, click on Insert Inline, then Done.