I uploaded this video one year ago to help another companies to integrate TCAdmin to WHMCS. The majority were using TCAdmin v1 module instead v2 so then I made this tutorial to help. He still working nowadays but you can add more features to him anyway, I hope this help you.
The tutorial is in portuguese (I'm brazilian) but just follow the steps.
We will use in WHMCS:
Servers (Configure your TCAdmin server)
Configurable Options (Configure Slots and Branded)
Products (Custom fields)
cPanel (servers/tcadmin_advanced2/custom.php) - (Optional, we will use custom.php to when create the service the server don't start to save server resources)
IMPORTANT
To add more features to your integration use TCAdmin Official Module Documentaiton
I hope this help you. Bye!