the tl;dr is just ask your friend for help.
the slightly longer version:
1. find items in game
2. list items for sale (you can use the search feature in the forum to see rough price estimate)
3. create thread listing said item (ft=for trade | iso=in search of | bin = buy it now)
4. pm user that has a fair offer in your thread
5. you drop item first because account is new and has zero fg
6. wait for user to send fg
7. say "t4t" in game once you've received the fg
note: if user leaves game after you drop item before he sends fg then you've been scammed. you can post a scammer accusation here:
https://forums.d2jsp.org/forum.php?f=250glgl