I suggest you read some tutorial on triggers basics and when they execute, and syntax used to create them.
This is example for PL SQL tutorial, very good one i used it to learn it:
http://www.tutorialspoint.com/plsql/plsql_triggers.htm[
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So calling procedure inside trigger is simple, you just write is as 1 line statement like any other, procedure name and input parameters if any and that's it.
Hope I helped.