There should be an instruction manual with the CRP.
There are also various "quick check" formulae for estimating drift, crosswind component, etc. They are in the PPL training books (or were in mine).
It's a good idea to use the one your school/club/instructor prefers, or you may confuse yourself.
I'm a simple "one in 60" person, but others have their preferred ways.
I'm not sure this is a "Computer/Internet" issue - you may fare better in the "Private Flying" Forum.