Hit N, the default for the crew skills panel, then click on the icon for what you want your companion to do, if its a craft skill, then you will be able to choose what you want to craft. if its a gathering or mission skill, you will be able to choose what type you will want to send them on
also for future reference, you can star sending them out on missions as soon as you get your companion, on my 2nd character i rushed through the class quests without doing any side quests and had my companion at level 6, then went through the side missions, was a lot easier this way