Do you have a zip-program? Like WinZip? I am assuming that you have a zip-program, when I am writing this text.
Let us assume your map is called killzone.
First, make a copy of it! Put the copy in a safe place. It is a back up!
Create a new, empty folder. Call it killzone
Inside this map you create a folder called maps.
Inside maps, you put your .map-file.
Start radiant. Open killzone.map. Yes, the file inside the folder maps.
Compile it (-bsp, -vis and –light).
Now you can see some new files, inside your killzone-folder. For example, there is a killzone.bsp file. Just leave them where they are. (If you ever re-compile the map, later on, these files will be re-written. That is normal, and they way it should be.)
Close radiant.
Your next step is to compress the folder killzone, and its content. Zip it!
When you have zipped it to killzone.zip you must rename it. Rename it to killzone.pk3.
Ok, this file (killzone.pk3) is it. You then copy it and paste it where it should be. That is, inside the folder called etmain (in your Wolfenstein – Enemy Territory folder).
Now, send the pk3 to your friends. Tell them to put it inside their etmain folder.
Or! You can also do this: Start a server with your new map killzone.pk3.
Password protected server.
Make sure players are able to join (give them the password to your server) and that download is possible (so they can connect to your server and download the pk3).
You must be aware that there are internet users and ET players that will try to download the map, if it is not password protected. What is wrong with that?, someone might ask. Nothing really. But there might be a problem if it is just a simple, made-for-fun map, that you do not want to distribute further.
If you have the map on a server that is not password protected, and if you are unlucky, someone might download it and host it on a different server. So, you might wake up one morning and find that there are ET-servers out there that run your map. It was perhaps only a simple map that you made for fun and that you had no intention whatsoever to make it public. Not nice, I know. But it might happen. It happend to me.
I made a simple room, with health/ammo racks and a water-tunnel under the floor. Two spawnpoints, one for axis and one for allies.
It was just for fun. To learn mapping.
I made the mistake to host it on my computer without password. I did it for like 30 minutes. It was a small sized map (<2Mb) and someone downloaded it. The next day it was out there. Brrr. 2-3 servers ran it. I felt so shamed. A crappy map with my name on it. (called Attack_beta).
Nobody runs it today, thankfully. Rest in peace attack_beta.
In sum: Make a zip (see above), rename it to .pk3. Put it in your etmain-folder. Start a password-protected server and allow download. Tell your friends to connect. And the shooting can begin!
Keep on mapping
// Loffy