How do you use the word supposed in a sentence?

Answer 1

Neither John or Mary cleaned their room, like they were supposed to do.

This is supposed to be a free concert.
You should not use "suppose to", since it's not correct. You can, however, use "supposed to", and you can use that in the same way you might use "should".

For example, "You were supposed to be here an hour ago" means "you should have been here an hour ago." In another example, "Their house is supposed to be on the next block" is about the same as saying "their house should be on the next block."

Answer 2

I suppose i can tidy my bedroom