Allow user to access

Allow user to access

Hi! everybody..
How can I allow user to access an especific module for instance: as administrator obviusly I can access to all one, but as a normally user I'd like to assign to access an specific module  in my case (Inventory and Purchase), by default they can access only to (Request, Solutions and my details).
 
Any idea, about it?
Please see attach file..
 
Thanks
ST

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