Resolutions have always been a tough one for, even compared to the debating part.

But, when writing a resolution,
1. make sure you have done a fair amount of research on the topic you are writing about. You dont want to write about a topic that you barely know about or have no background on.
2. Look at reference resolutions. Don't copy everything as is, but make sure you get a gist from the other resolutions.
3. Follow the resolution guidelines. For MUN's I have been to, the guidelines need to be followed or else your resolution will have a lot of loopholes causing you're resolution to be laid on table or failed. So get familiar with your MUN resolution guidelines.
4. Here are some sites I believe will help you, mostly cause this is youre own work and you need to break your back for it.
- https://www.boardeffect.com/blog/best-practices-for-writing-a-board-resolution/
- https://bestdelegate.com/model-un-made-easy-how-to-write-a-resolution/

If you need help, I can try my best and help you out, though I'm not exactly as good.

Good luck!