If you want to write a PCR: using PE02 to do that.
You should reference 2 useful links below to know how to write it:
If you want to check the processing class of wage type: VWTCL.
You should read Standard PRCs to have more deeply understand: eg: X024 Gross Input and Storage.
If you want to know the meaning of processing class: go to T-Code: SM31 or Sm30 then input V_512W_D. you will have detail processing class of wage type.
As mentioned by Woody, study your current PCRs and how they are called in your schemas.
Also execute Time Evaluation for one employee, in "Test" mode and with the Log/Protocol turned on. Explore the log and try to follow what happens. Do the same for Payroll.
Read the documentation available in pe04, or elsewhere on the web.
P.S. : SAP also offers courses on Schema and Rule writing.
I am not aware of any course to write PCR - most SAP courses just discuss standard schema and concepts behind PCRs
Please see following tutorials
Maybe of use