Invaders Surge Inland's Healthy Island effect says: "On a Coastal land on Each Board: Move 1 Town one or two lands Inland."
You move the Town from a Coastal land once or twice, moving further inland (farther from the coast) each time. If there is only one option, it is made automatically for you.
Sometimes, after you have moved a Town once, there is no way to move it a second time; this happens, for instance, on Board A if you move from land 3 to land 4. You cannot then move it to land 5, since land 5 is not further inland than land 4. (Both are adjacent to a Coastal land.)
The Town does enter intermediate lands.