Thick gloves and a good pair of seccateurs or shears.
Gradually cut all the long shoots back until you've reached the main root area. Then get the help of a strong man (if you're female) to help dig the roots out because the can go very deep and spread a long way.
Try and get every last bit of root out as they're very good at regenerating themselves.
cut back the majority of it but leave a bit with some leaf on and treat with weedkiller. Grazon 90 as suggested is a good one but there are plenty of others. When its died off dig the root out as much as you can then burn or dispose of. Don't put it in your compost heap nor the bits you cut off cos they will never go away
They are very difficult to get rid of. I did for mine by 2-3 applications of Roundup. That finished 99% of it, but even so, there were still fresh little sroutings coming up off the root. A spray of Roundup does for them as well.
So, about a year after I started, I'm confident it's all gone!