Once you let me know what the of the file is, I can help you with the steps to open it or use what's inside.
To give you the most helpful guide, could you clarify what is inside that file or what it's for? For example, ajb05920.rar
A guide for a specific game mod, save file, or asset pack? Once you let me know what the of
Instructions for a specific industrial or engineering part? ajb05920.rar