XD Waaaaaaaaaaaaaayyyyyyyyyyyy OFF TOPIC! XD But, flower, seriously, the most popular (and possibly easiest) downloads, are in mediafire. Actually, MOST of the download maps are in mediafire.
Like Ruby said, just look for a map that interests you, click the link (probably leads you to the mediafire download) click download, unzip the file, and usually, put everything into the exports folder in your FH folder. Sometimes you'll need to put something somewhere else, but usually then, there's a README in the download.
So, thats how you download and install maps.