Question

where was toto kept immediately after grandfather got him and why

Answer 1

He was tied securely to a peg because his presence was to be kept a secret from the writer's grandmother as she abhorred animals. 

Answer 2

grandfather bought toto from a tonga driver for the sum of 5 rupees. The Tonga driver used to keep the little red monkey tied to a feeding trough and the monkey looked so out of place there that grandfather decided he would add a little fellow to this private zoo. grandmother don't like the habit of grandfather to bring new pets. so it was decided that toto's Presence should be kept a secret from her until she was in a particularly good mood. grandfather and the narrator put him away in a little closet opening thought to a peg fastened into the wall . later they found the place was destroyed by toto. he then kept it in a private zoo.
hope you understand.......