The sales process consists of you transferring ownership to an address the buyer provides you after they pay you; it's not programmatic. The fastest/simplest way to sell is probably to list your star on opensea.io, though there's also a marketplace group on urbit.
log into bridge w/metamask or whatever you use -> click on your star's name -> click 'id' in the menu that appears -> click 'transfer point' in the id menu -> input the ethereum address you want to send the star to and click 'generate and sign transaction'. did you really spend several hours trying to figure that out lmao