You can write your topic however you want, but you need to answer these questions:
What do you want to achieve? Keep it simple and clear!
I want to create a game icon for my game.
What is the issue? Include enough details if possible!
Well, this is my first game. I don’t know where to start.
What solutions have you thought of so far?
None, im making this post in advance.
After that, you should include more details if you have any. Try to make your topic as descriptive as possible, so that it’s easier for people to help you!
Easy way: Just put some text into Photopea, edit it a bit to make it look interesting and fit your game aesthetic, and if you’re feeling creative experiment with adding a few shapes, graphic elements (such as particles, glow, etc.), gradients, logo, etc.
Medium way: Create a job post in the talent hub and try to get an experienced artist/GFX designer to do it for you.
Hard way: If you think you have the skills then try doing it all by yourself using tools like Photopea/Photoshop/Illustrator/Inkscape (for effects/editing), Blender (if you want a 3D Roblox GFX), or drawing software like Paint Tool Sai (if you want a 2D drawn effect).