To create a side post for your carport, measure out your beam height and mark it out squarely on the end of the post. Then down the side of the post, measure out how thick the beam will be so that it sits in squarely on the post.
You'll need a friend to help you put the posts into the supports that you've already made. Use a spirit level to make sure the posts are level or your carport won't be straight. Place the post in the middle of the support with the cut outs facing outwards.
When your post is level, screw in the post to the support. Brace your posts with timber and clamps so it doesn't move while you're finishing.
With the help of a friend, lift up your pre-cut beams and nail them into the cut outs at the top of your fixed posts, just to hold them in place. Make sure the beams have been cut on a 45° mitre to get a nice sharp corner when you join them together.
Once your beams are all in place, screw them together. Put the batten screws in at different heights so that they don't hit each other at the joins. Continue on nailing and screwing in your beams until you've finished your carport framework.