Your Circuit Training

I Want To Start Circuit Training In My House And I Was Wondering If Ya'll Had Any Ideas For The Stations I Dont Own Any Workout Machines (except For Weights) I Have A Spacious Upstairs And A Full Flight Of Stairs Plz Give Me Ideas Thx! Also I Have Asthma And Grass Allergies So I Would Prefer Staying Indoors
Also If You Could Explain What The Exercises Are That Would Help Too :)