1. Go to your project page on CurseForge.
2. Click "Project managment" on the right.
3. Click "Upload image".
Also, nobody is going to PM you about helping you with Lua coding. Not only does nobody have time to provide free private tutoring to everyone who asks, but there's no way for anyone to even know if they can help you before wasting their time and yours PMing you to hear the question. The forums exist for a reason. Post your question on the forum, and hundreds of people can see it. Someone who (a) actually knows the answer, and (b) has time to give you the answer will probably reply.