2001 Toyota Camry Check Engine Light

My check engine light came on after a oil change .. I am wondering where I can get the tool to diagnose this ... Heard the video but was not able to see it ... I want to know if there is a check list that I can look at that will give me an idea because I really don't have the money for any expensive work . I really don't want to go back to the oil change place because I have heard bad things about them.

Thanks