On your reference I will tell you step by step way to book tickets of Karnataka State Road Transport Corporation through online medium and will also provide you Gadag booking centre address.

Here is the address of booking centre

KSRTC Ticket Booking Centre
Tanga Koot, Gadag, Karnataka 582101

Phone:-
083722 10688

If you want to book tickets online this process will help you

Go to official site of Karnataka State Road Transport Corporation which looks like this

Karnataka State Road Transport Corporation



There at middle left hand side page
You can see section of book tickets
There fill the required information

Address:-
Karnataka State Road Transport Corporation
No.115, K H Road, Shanthinagar, Bangalore - 560027, Near Big Bazaar

Phone:-
+(91)-80-22221321, 22221332
+(91)-80-22223424