I'm not sure if you're the same user who asked this in New Members Introductions. If no , I'll briefly repeat what I put there.
It's basically what TommyBoy said. Click on the sticky-thread that is titled, "Bluelight Mobile." If you look at the first post ut gives you options of "full site," or "mobile version,". Click "Full Site." N you'll be transferred to the full version.
I would recommending bookmarking / favouriting the Bluelight Mobile thread , encase BL resets itself back to mobile version- or if you ever wish to transfer back to mobile version.
Once you are on the "full site" version, go to "Other Drugs" either by the "forum" or "Home" tags, which both list the sub-forums.
Click on "Other Drugs," then "New Thread" you will them see a "prefix" menu, click that n one of the drop- down topics ie Heroin, opiates etc.
There you are - you're able to create your thread. Hope that helps somewhat.
Evey