1. Get Notepad
Tech teams are located in seperate files for each country in db/tech/teams for example teams_usa is the file for the US-Techteams.
In the file each tech_team is discribed in one line, with different values, seperated by an ";"
The Values are a number, the Name, the picture used, the Skill, start year, end year, and speciality 1 to whatever.
2. To make a new tech_team start with making a copy of one of the lines (a klone of one existing tech teams) as a base.
3. Change the number in the beginning (each tech team needs an individual number). The last number in the US file is 240035 so you could try the 240036 for your new team.
HOWEVER, it may be the case, that a creator of a mod didn't leave the sucsessive numbers free and you will get an error message saying something like "XYZ alredy used". If that happens to you, you have to search for a free number usually by try and error (using incredibble high number usually helps).
4. At this point you technically made a new tech_team, although it is nothing but a clone of an existing one. To make it a "new" tech team you just have to change Name, Skill and specialitys. Pretty self explanatory.
5. The Pic_name is referring to a picture in gfx/interface/pics pictures for tech teams have to be 96x96 pixels and must be in .bmp formate.