While we can help you with specific problems, we cannot teach you how to use Access, in general. This website isn't really set-up for that.
Creating queries is one of the most fundamental, basic, and important things you use in Access.
There are tons of tutorials, books, and videos out there that can teach you those things. Most can be found very quickly with a Google or YouTube search.
Try searching on: Creating queries in Access
and then after that you can search for: Creating Calculated Fields in Access Query
Also, any beginning Access book will contain all these details.
All these options are much more detailed than anything we can provide in a response here.