Warm greetings @maddy 
Welcome to the forum- thanks for your question! While I don’t personally use a familiar (a creature/demon bound by contract) in my practice, I know it is a subject that has come up quite a few times here in the forum. There are many witches who choose to call upon outside presences in their practice- from familiars to spirit/power animals, to guardian angles, to deities, and more!
You can find some helpful advice about the difference between pets and familiars (as well as some tips about forming a contract with a familiar or connect with a spirit animal) in the following posts:
→ Familiars and a Pet
→ Familiar Spirits and Power Animals: What’s the Difference?
→ How to Find Familiar/Spirit Animal?
Good luck and blessed be, Maddy! 