Welcome! Depends on how bad and with what. Most oil change shops can try to flush it. If that doesn't work, a radiator shop my be able to boil it out, which would require removal. But at that point it might be cheaper to just go with a new radiator. Many times clogged radiators, when vatted, reveal leaks due to rust, and are not really viable to repair. Good luck, and keep us posted on how it goes.