For sealing the corners of the camper, doors, cargo holes, windows, you use butyl sealing tape. Then after a while (a few months when it is warm out) you can use Dicor non leveling sealant with a soapy wet finger to seal the exposed edge so dirt does not stick. This is after the ozz'ing stops
Like this. This is a slide corner, but same thing on widow, door or cargo hole. Scrap and clean the corner. Mineral spirits on a rag and scrub will help get ride of stuck on material that will not scrape clean. Then use a high flash solvent to get rid of the traces of oily mineral spirits.
You can see the dirt path here where the older putty tape unstuck. I was lucky, water it did not get in this way yet. But not all are that lucky.
Once cleaned up, roll it down and remove the release liner
It you want added protection, you can put small strips in the corrugated spots
When you tighten up the flange, it will ozz out, or should ozz when it is warm enough
Trim with plastic scraper. A ball waded up and stick and yank helps gets excess unstuck.
Butyl rubber sealing tape costs a little more then "putty" tape, but it lasts longer and resits cracking better over time. If you stretch butyl tape, it will string and pull like taffy. If you pull on putty tape, it will stretch a little a then snap off. There is a lot of putty tape for sale, if you only plan on 4 to 5 years, it will work. Some go longer. For $3 to $5 more, butyl can be bought and last 3 plus times longer.
Water leaks, look at how the roof seals to the side of the camper or how the corner molding is sealed to the top of the roof or the sides of the camper. Over time that seal breaks down and water gets in. A common death of a camper is the putty tape gets splits and cracks under the molding. Then it allows water to get in. Screws holding the molding on rust and then water wicks in the screw holes. Soon infection keep going after each rain. If the screw into the wood is rusty, moisture has been there. Goo on the screw with rust under it, means wet is still there as rot is active.
Mine has a rubber roof so I do not know exactly what yours looks like however the method of the roof to the side or the roof to the back wall or the camper corners is similar. Everything works great until the sealants start breaking down. On the rubber roofs, there is caulking used to help seal the rubber to the side modeling that has butyl under the molding. while the butyl may be OK, the caulk can split and water works it way to the screws. The rusting screws (a zillion of them) start making holes into the wood. Soon water infiltrates.
Hope this helps