The gasket is self adhesive. The old gasket can easily be pulled of by hand. As mentioned below clean the area of any leftovers from the old gasket or glue and put a new strip on. I use the side of a screwdriver to put some firm pressure on the new gasket to make it really stick in place.
Part of the gasket fluff has partially detached and is causing the daggerboard to partially jam when trying to raise or lower. What is the best way to remove the old gasket and what is the best way/best glue to attach a new gasket.