During business hours (5-8, Monday-Friday), you can simply take the elevator from the 1st floor.
After hours though, you can't tell the elevator to go from the 1st floor to the 4th. You can, however, call the elevator to the 4th floor from 4th floor landing.
So, someone can walk up the stairs, go through the gates on the 3rd floor, and call the elevator from the 4th floor. If someone is in the elevator, it'll take them to the 4th floor!