You put them between the cup and the frame, when you screw them in.
So, if the cups have not been removed, in theory just sticking the new cranks in would be fine, I reckon.
@Dammit started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
You put them between the cup and the frame, when you screw them in.
So, if the cups have not been removed, in theory just sticking the new cranks in would be fine, I reckon.