I'm trying to get an AI to drive to passenger stations, but I can't tell it to, the only options are for it to run to trackmarks. Is there a command I need to download first?
Your initial description did not give enough information about your problem.
One possibility is that the stations you are using may not be passenger enabled. This is certainly true with stations built using just platform splines and scenery buildings. Are you using a passenger enabled track such as those by AJS? Without this there will be no "target" for the Drive To command.
Another possibility is that the Drive To driver command has not be enabled in the Driver Command Rule in the Session Editor.