Go into the folder of your installation of SH3 where you want to install this to. That might look like "
D:\SilentHunterIII\"
If you do not know the path then take
S3F (http://www.donitzeliteflotilla.com/forum/index.php?msg=3708) - it will show you!
Next, go into the sub-folder "
data\".
READ: Is it an SP or an MP mission?
Then go into either into sub-folder:
a) SingleMissions, e.g. "D:\SilentHunterIII\data\SingleMissions\"
or respectively
b) MultiMissions, e.g. "D:\SilentHunterIII\data\MultiMissions\"
Think: What is your selected language in the game?
a) Is it English? Then go into sub-directory "English".
b) Is it German? Then go into sub-directory "German".
READ: What is the EXACT filename of the mission?
IF there is NO folder with that name already included create a sub-folder of the EXACT SAME NAME:
Example#1:
You run the game in English and the SP-mission file-name is "testmission.mis"
The folder-name MUST be "...\SilentHunterIII\data\SingleMissions\English\testmission"
Example#2:
You run game in German and the MP-mission file-name is "Schleichfahrt.mis"
The folder-name MUST be "...\SilentHunterIII\data\MultiMissions\German\Schleichfahrt"
ELSE: Copy that folder (which itself includes the .mis file) into that location that you have just dived into.
Next, start your SH3-installation (the one you have installed this into).
IF it is an MP-mission
Make sure you have a network-connection running.
Otherwise you can only play that MP-mission alone.
Start the SH3 option for Multiplayer on LAN: Multiplayer, Wolfpack (whatever it is called in your setup).
(This option is for instance called "RUDELANGRIFF" in the GWM-Mod).
ELSE Click on SINGLE MISSION
Select the mission. A mission with that name should show up in that list.
Make further settings to your liking. Go ahead to run that mission.
Start it and enjoy - either alone or together with your wolfpack-friends!