find a post, comment or message the person. meet in game, trade gold.
Typically join date/fg amount dictates who goes first or whos comfortable going first.
So most people will absolutely not send first for a random that just joined. scams happen for noobs all the time, not so much on the d2 side of things but its wildly easy if the guys a dick.
so just be cautious.
Theres a mediator option, a trusted third party to collect goods and gold and make the trade himself, i suggest you try that.