Someone comes up with an idea for a bill. This person can be anyone, from a child to the president!
The idea for the bill is brought to a member of Congress and a bill is written. If a senator writes the bill, the bill will then be sent to a committee in the Senate, and vice versa if the bill was written by a member of the House of Representatives.
The bill is introduced to a committee in the House of Representatives where members of the committee debate and amend the bill.