There are many things you can do to improve the quality of your aim. Here is a quick rundown of the most obvious: strength, a relaxed bow arm with a very slight bend, a relaxed grip, a focus on the spot and not the pin, breathing out very slowly while aiming and making a surprise release.
Those are the obvious improvements. Now we need to get into the suggestions that aren't as obvious on how to aim a bow better.
First, let's forget about shooting and see what it looks like. If you aren't holding steady under these conditions, you have some simple work to do first. Relaxation and proper positioning is the key to steady aiming. Make sure that your draw length is correct and that your bow fits. With a very slight bend in your bow arm (just enough to unlock your elbow), make sure your other elbow (string side) points straight behind you at full draw. That forearm should be parallel with the arrow. If it points even a tiny bit behind you, your draw length is too long. If it points in front of you, your draw length is too short.
Relaxation is next. You want every part of your body to remain relaxed. You might be surprised to find that tension starts from the ground up. It is very hard to relax your bow arm if your legs are tense. Seems odd, but it's true. Make sure everything is relaxed: feet, legs, stomach, chest, bow arm, bow hand and shoulders. Keep your shoulder down (not pushed up by the draw force) so you can oppose the draw force with your skeleton rather than entirely with your muscles.
The only muscles that should feel the tension of the shot are your upper back muscles that lock your release arm back into a steady position. Using this very stable muscle group will permit you to hold steady.
The only thing still required with how to aim a bow better is the strength to relax fully. Strength comes with practice, a prime reason why you should shoot regularly for at least two months leading up to the bow season and then at least three times per week during the season. You have to keep those muscles strong so they can support the shot without tension.
Easy On The Trigger
If, however, you find that you can hold the bow very still at full draw when you have no intent to shoot, the problem is more difficult to fix. Not harder to explain, just harder to make yourself do. The solution requires that you learn to make a surprise release so you can take advantage of that steady aim with good accuracy.
You must keep your mind off the shot timing. This is very important toward calming your nerves. Don't worry about when the bow will fire, but rather focus all your mental energy on relaxing and just pulling the trigger slowly. Don't worry about where the pin is, focus on the spot and the pin will take care of itself.
Move your entire upper body (not just your bow arm) to keep the pin on the spot. The shot will take care of itself. If you will take this medicine and give it an honest chance to do its work, you will be amazed by how well you can shoot a bow.
Remember, it starts with proper form, advances to the need for muscle strength and finally ends with the ability to make a surprise release. You have time between now and the season to learn how to aim a bow better.