Install mods here by simply copying the .bab file to the folder and adding their name to bablist.txt. You can modify the .bab files with any text editor.

Documentation:

Each .bab file is composed of at least four sections; all but the first can have multiple variants.

[Info]
Within the info section, you must have several things.
Name=This is where you put the name of the character.
DispName=This is the name that shows up in the baby select screen.
Gender=Self-explanatory.
Difficulty=This is where you rate the difficulty. The official difficulties are Easy, Normal, and Hard, though you can technically put anything you want here.
Likes=Self-explanatory.
Dislikes=Self-explanatory.
Other=Any other info you'd like the player to know about your character.

[Choice0]
This is the opening Choose Your Own Adventure-style section. Further sections with this title will have another number replace the '0'. Section zero is always the beginning section.
Desc=This is the main text on the screen.
Opt0=This is the text of the first option. All three (Opt0, Opt1, Opt2) are required.
Opt0n=This is the section you'll be directed to if you choose this option. Positive numbers represent further [Choice#] blocks, -1 represents moving on to the Domination section, and 0 or not including this option at all (the latter is preferred) represents a failed choice/game over screen.
Opt0fail=This is the text that occurs if you get a Game Over. This only needs to be in the file if choosing an option leads to a Game Over.

[Dom0]
This is the first Domination section (where you use tools to baby your target). It's numbered in the same way as the choice sections.
Desc=Same as Choice.
Opt0=This is the failure text for that option. It only needs to be included if an answer is wrong.
Opt0n=This works the exact same way as Choice except for one part. You can actually have any negative number here rather than only being able to choose -1. Negative numbers lead to the Victory section, meaning that you can have multiple Victory options. -1 corresponds to Victory1, -2 to Victory2, etc.
Fail=This is the Game Over text if you fail on this option.

[Victory1]
This is the "win" condition section. It is useful to know that as the previous section uses negative numbers to denote moving on to the Victory section, zero cannot be used. Instead, the number one is the first in the Victory section.
Desc=This is the only needed piece of the Victory section. It's the same as the others.