How do I speed up my video please Answer? PLEASE!!!!!!!?

so I want to know how to speed up my video my program that I'm using is camtasia studio I made a video but My brother put in music and he sped it up but he didn't tell me how he did it so can somebody tell me easily so that I can understand I'm only 12 so if you say it really confusing then that won't help me at all Oh! and tell me how to put in music :) thanks