Your truck should be towing ready. It should have a brake controller for electric brakes in the camper. If your truck does not have the brake controller, you'll need to get an after market one installed before you tow. Otherwise you will have no trailer brakes. And the F150 will not have enough braking power to brake for both the truck and the trailer by itself. Plus, it's illegal to tow a trailer of that weight with no brakes. And this in every State.
Second, you will need a weight distribution hitch also. I suggest, if your grandmother has a weight distribution hitch she used on her vehicles, that you use it too. You will have to adjust the tension to match your tow vehicle, but the entire hitch system (whatever it is) should be all complete. If it's the old style Reese with chains on the bars, then adjusting the tension will be pretty easy, just lengthen or shorten the chains. If it's an Euql-i-zer system, then you many need to adjust the height of the L-brackets on the trailer frame.
Depending on the weight distribution system, you'll need sway control too. If an Equal-i-zer or Reese Dual Cam, it has built in sway control. If you go with a Blue ox, or the standard bars with chains, you'll need the separate friction sway bar. The existing trailer and existing hitch will be set up already for it.
Hopefully, she will give you the Weight Distribution Hitch she used. If not, you'll need to get one and get it fitted before towing.
Other than properly inflated tires, there's not much more you can do to prepare your truck.
You'll need to check out the trailer too. Make sure tires look good, and are aired up to max pressure. Check brakes, lights, and take it around the block before heading out long distance. Make sure it handles safe and your truck can handle it OK.
Your truck will be working to pull that trailer. Expect your fuel mileage to drop a bunch when towing. But I think you'll be able to get that trailer home.
Good luck.