Now of course this is asuming you have in fact EXPORTED your map, if you have not done this, then you must do it before you follow the next steps, you go about doing that by opening your map in the object maker, clicking export and then wait untill it has finished exporting.
Ok, in your exports folder, there should be a few file types.
.fho
.fhm
.fhs
Now, the .fho file, which is the file type, is exported objects, if you have NOT used custom meshes, and only those in game, you need not worry about them BUT, if you have, you need to gather those together.
The .fhm files are the exported maps. Containing heightmaps, textures and so on, these are the most important, you MUST have your maps fhm file in your download for it to have any chance of working.
Now the fhs file is for custom skies, if you have not made one, obviously it wont export one, so you needn't worry if there's not one there, the same goes for .fhw files.
Ok, now what you do is gather the .fhm file, and any other of the above you may think implies to you, you create a new folder on your desktop, save it as what you like, then place those meshes inside it.
What you do next, is right click, scroll down to send to, then click zipped file.
A file with a little zipper along its side should appear with the same name as the original file.
Now you upload it to a sharing site, such as mediafire or sendspace, it's up to you which one you use.
Now, you give the link to the download to the people you want to see it, instructing them to put all of the files inside the folder in exports.
Hope this has helped you.