Would like to buy a listed item cannot seem to figure out how this is done will not let me make an offer buy it now not available
sounds like someone beat you to it
Try contacting the seller directly. There is a link in the box at the top of the ad denoting who the seller is along with their feedback. Not all ads have a Buy It Now option. 
Keep trying your doing something wrong.
If you keep having a problem open a help ticket and get Tammy to help you out