As the creator of an ever-growing "Map Suggestions" thread on DRO as well as someone who does his own ports, I thought I'd just give everyone a guide. Enjoy!

Start here:

http://www.armaholic.com/page.php?id=16369
This is a .pbo unpacker. It's small and easy, don't worry about it.

Once you've got that, go to:
YourName\Documents\Local\ArmA3-OtherProfiles\YourGameName\Saved\steamMPMissions\

Find any DRO/DCO you've got, open the .pbo with your handy download from earlier. Copy the contents, then go to:
YourName\Documents\Local\ArmA3-OtherProfiles\YourGameName\mpMissions\

Make a new folder (or create a blank Eden map, save it with the name "DROPort" or whatever.)
The extension at the end of the folder will say which map it is. If you don't know your map extension definitely make a blank Eden map first, as it'll save with the extension tacked on.

It'll look like: DROPort.tem_ihantalaw, as a folder. Paste the .pbo contents into this folder.

Last but not least, you need to glitch-proof your port. Do this by opening ArmA and firing up Eden again. Find your "DROPort" save and open it up. If you've done the previous steps correctly, you should see some objects/assets along the left. Specifically, some civilians and some props.

Find these assets, they are usually far off the map somewhere in the out-of-bounds void. You want to move these guys over to somewhere reasonable on the map proper. There's a few ways you can do this, do it however makes you happiest.

https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1612412247

If you're not used to Eden, my dummy way (because cut/paste sometimes does weird things in Eden) is to create a unit where you want the setup area to be. If you right-click on one of the "Civilian"s on the left, you can click "Go Here" and it'll move the camera over to it. Then click on the dummy unit and right-click and hold to move the camera around until you see where it is, way off in the distance (probably). Select all the objects, click and hold then move the camera off in the direction your dummy unit was. You can speed this up by holding Alt and Shift. If you use Q to gain some altitude I believe that also helps the camera move speed.

https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1612412325
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1612412382

Note: Your objects might be floating like weirdos off the ground. Fix this by selecting all those objects again and one of the options (under "Transform") should be "Snap to Surface." Not doing this may cause you some problems.

https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1612412407

Once all that's been done and you're happy with your little team setup area, your port should be ready to go! SAVE YOUR FILE. Then... fire up your multiplayer local server, select the map you ported to, and enjoy!