Help!!

My father recently bought me a knight dk20s heat press machine for i cant start my own little summer buisness in making shirts.Im preety kind of new to this buisness so i have some questions over operating a heat press.

1.Do you have to use any protective coating over the top of the shirt when you're printing a t shirt.or at the bottom such as a clothing or anything?

2.I have paper to make the t shirts but i can only make it on white shirts are there other papers which let you print on colored shirts?

3.What are some tips over getting a nice shirt?

Any information or tips would be a great help!
Thanks