Post your custom missions in this thread. You can upload them in the
Subsim Downloads Cold Waters custom missions section and then link from your post here to your custom mission.
If you need access to upload your custom mission, just PM me.
Video How to install Custom Missions.
Note, this applies to missions created by me, since there is no standard for creating the single##.txt files. I give the file that has the briefing a temp name of BRIEFING_single##.txt so the player can tell them apart.