He likes to sit on his arse all day and do nothing.

He is sitting on his arse all day.

He sits on his arse all day and does nothing.

I love to sit on someone's wheel during a race.

From where one sits, the view of the mountains is breathtaking.

From where one is sitting, the view of the city is breathtaking.

When the teacher mentioned the upcoming field trip, the students sat up and took notice.

I told him to sit his ass down and listen.

He sits his ass down on the couch.

I am sitting my ass down on the couch.