test modified freebsd source

[Peter Harris]

Hi guys, I am currently pursuing my internship and new to freebsd (switched from Ubuntu). Its gonna get used at my work. I have the responsibility to make some modifications and customise source tree as per the demands.Can i get some suggestions on what would be the best way to test the changes i make? Majorly I need to make changes to the current commands and some minor changes to the kernal. I haven't done such a task before (like building a complete OS) so i am pretty much clueless. Would really appreciate getting some help. Kind regards, Peter