Renting out a room. We rent the house. What do?

I wanna write up some sort of contract of terms for someone renting out a room in my house. My current lease allows for this and says any tenants are at will of the lessee(me) and that I am essentially their landlord.

How can I go about doing this? Do I just write a separate lease for the terms agreed on and have it signed just as the homeowners did for me?

I am in Austin (travis co. obviously)