I've already done the 'Destroy Confederation trader (?) Fleet' mission, but I can't find the next. Do I need a higher combat rating? I've now Competent.

That mission is not one of the big strings. I think your combat rating has to be deadly, though, and I also think you have to be an Upstanding Citizen at a Rebel planet to get the mission. I'm not completely sure though.

Look for a mission in the bars when someone passing by your table drops a napkin telling you to go to dock 94 or something like that. Those are the missions you want.

Does it give walkthroughs for EV?

Destroy Confederation TRAITOR. It's not that hard to spell. You see it in the game.

It's difficult to say what's next. Like what Destroyer E said, it's not a big mission string. It will help your combat rating improve and will help your standing with them. Plus there is a random percentage to get the first mission of a major string. So just keep doing more missions until you get something important.