If I have a mission file in written form..

_{[MAIN]
MAP Italy_DF/load.ini
TIME 17.5
CloudType 4
CloudHeight 500.0
army 1
playerNum 0
[Wing]
261Squadronfe03
261Squadronfe11
356squadriglia01
261Squadronfe21
g0113
261Squadronfe00
261Squadronfe12
g0110
261Squadronfe31
g0111
[261Squadronfe03]
Planes 1
Skill 2
Class air.P_40SUKAISVOLOCH2B... etc}

Don't I need the Properties & Mision files? Where do I put this stuff? I never did a mission like thsi and I always wondered how it worked.

What you have there is the basic mission file. save it as "NewMission.mis" and put it somewhere in your missions folder. You can then access it using the FMB (or if you put it in an existing folder under 'single' you could select it in the game).
In the FMB you can type in the mission name and description. The properties file is auto-generated when you save the mission from FMB.

What you have posted looks like a Coop mission, so it should be placed in a folder in:

C:\Program Files\Ubisoft\IL-2 Sturmovik 1946\Missions\Net\coop