Ah, no worries deary, I shall explain it f'er ye.
First things first, find a map pack that ye wish to download. Make sure that this map download is on a credible download site, like Mediafire or Dropbox. Do NOT press any ad buttons or things that are not labeled as the actual map download button. Make sure ye read b'fore ye click anything.
If it leads ye to adfly, a sponsor site that redirects ye to the website that y'er heading to, make sure that do not click the ad in the center of the site, but the "Skip Ad" button on the top right hand corner. This button will appear after five seconds.
Once downloaded, go into y'er Downloads folder on y'er File Explorer. Open the newly downloaded map pack, and check the contents. There will most likely be one or two folders, each labeled with where the files inside need to go. If there is a Read Me included, do read it as it may contain some important information regarding the map pack.
One of the folders that should be included is a folder named "Place in Exports" or something similar to this. Open it up and highlight all ye see inside. Right click and select the option "Copy". Head to y'er FeralHeart folder and find the folder labeled "exports" and open it. Right click in an empty space inside the folder and click the option "Paste". The computer will begin transferring the files into the folder.
Now, 'gain, head back to the downloaded map folder and check to see if there are any MP3 files. MP3 files are important to y'er map as they will play some nice tunes to match the theme of the map. If there are any MP3s copy them and head to the "music" folder found in "media". The "media" folder is found in the main FeralHeart folder.
Once 'gain, ye will need to head back to the download folder {tiring, yes?}. This time, ye will be searching f'er a file named "music.cgf". This file ye will need to open with a program like Notepad, or something similar that can open, read, and edit text. Copy all the codings found in the cgf file and head to y'er FeralHeart folder. There should be a similar file found directly in this folder. Open it up and scroll to the bottom of the text. Make a new line and paste the content ye copied from the downloaded music.cgf. Save and close the file.
Then, head on to the game and check Cape of Distant Worlds. A new portal should be found there. And that is it! Ye just completed downloading a map! I hope this helped ye deary, if ye need any help or find any of this confusing, just let me know and I shall do m'best to explain further.