You unscrew the retaining ring with appropriate tool, there is a rubber seal under the ring then the front element will come out.
Problem is the haze is usually on the softer middle lens that requires taking the barrel out.
Haze is etched in and requires specialised equipment to clean. These lenses are fiddly and easy to scratch.
If it's not bad, then live with it. It's only sun flare that will impact on. A yellow filter and lens hood will help.
If it needs cleaning I would send it to someone who knows what they are doing and have corrected equipment. These lenses are very good and are increasingly in value, so worth the expense.