Just going to make sure, but are you sure you placed all .fhm, .fho, .fhs (if provided) and .fhw (if provided) into Local Disk (C:) \\ FeralHeart \\ exports. If you have then you should be able to see and enter the map through it's portal. Thing is, the custom map portals are so difficult to see in Cape of Distant Worlds because of how transparent and how dark the area is. The first portal will be found directly to your left or right, behind the small hill where the stone arches are.
If you're still having a hard time finding them, I suggest you download and install my portal mod to the game. Custom Portals - Improved (https://feral-heart.com/smf/index.php?topic=58069.0)
A few reminders.
Most people put the files together into either a .zip or .rar file. You as a user must also unpack/extract/unzip or whatever you want to call it before you actually put them in your game. Please make sure you unzip the folder before installing them since some people forget this.
Do you actually put the maps into the correct game? In theory you could have an endless amount of different FH games/folders on your computer as long as you have space for such, if you install the maps into a copy of the game you aren't even running the maps will not show since the game does only locate maps within it's own folder.
If you are one hundered percent certain that you do everything correctly when it comes to the installing of custom maps it could be a chance that the map creator did not create portals properly, but if you know that others can play it then you are most likely doing something wrong and need to track back your steps until you do it right.
the .fhm file is really the only thing that matters when it comes to getting a portal in cape, so it must be used the right way and place in the correct place, otherwise no portal will show.