Creating a Mod with new tables/database fields

[komirad]

I know PHP/MySQL.
I am using VB 3.7.2
I have installed mods.
I have been looking through the code of some of the mods and made some minor changes to them.

I've read https://vborg.vbsupport.ru/showthread.php?t=98009 and https://vborg.vbsupport.ru/showthread.php?t=62164
but there's no explaination of where the installation code is.

I want to write a custom mod for my forums.
I notice there's an xml file that's used to install the mods.
How do I create the install file?

Let's say my mod requires me to create/edit tables on the database.
Where do I put the SQL code? Do I write it on the XML install file manually?
Or is there a way to write the install code in PHP then export it using the Manage Products page?