I haven't installed the rubber seal yet, but I believe it slides into the channel. There's an opening in the center of the channel that I believe is used to install the seal, inserting each end from that opening. The seal will have to be bent in the middle to do that. The process will be much like installing the windlace on the 49 and later trucks that use a retaining channel (not like the earlier retainer that's screwed in place), and is shown in the service manual. Removing the reveal molding will give you more room to work, as it's going to be pretty tight even with the reveal molding removed.
