Oh, I understand now. My apologies for my late reply, I was intending on a more skilled map maker to fill you in. I have just given it a go now and I will list my steps.
As I have not imported any objects made by the Community that are not supplied by the game, You will have to tell your friends the exact location said files need to be in etc. As if they were importing them into the game.
To edit the maps you will need to locate 4 things in the Terrain's folder and copy them into the shareable zip/rar file (In this case I will be using my map as Test). You will need your Height map(s), Your mask/color map(s) obviously as a copy. Then you will find a folder named after your map(s) for this case mine is Test. Copy this folder as well, after that there will be a .map file named after said map (Test.map). These are the files the Map Creator needs in the game to edit your maps.
(For a clear pathway I will list it here: :C - Feralheart - Media - Terrains. Copy: 'Test'.png [Height map], TestM.png [Mask/Color map], Test [Folder] and Test.map )
If you have multiple maps you may need to go in and find each 4 'files/folders' for each map you wish to add together. Again, You will need to add each of your imported Objects folders into the same folder you wish to send your friends so they can see the placement of the downloaded objects, otherwise they will show as invisible (Nothing there).
I hope this was clear enough love, I am not good at instructions ;o;