I cannot get the Phys gun or Access the '"q"' menu to select items at all.

I press q and nothing happens.So I walk around the levels without being able to do anything which is very annoying because firstly I payed for GMod and can’t use it properly and secondly I seem to be one of very few on the internet who have posted this.I have no ideas how to resolve this since I have tried everything.I have a Lenovo Laptop G505 with an AMD A6 Quad core chip and am running windows 8.1.Please help because everyone I know is raving about GMOD and I can’t do the fundamentals with it , which is put down/place objects and make them do silly or amazing things!!HELP!!!

Are you using a touch pad?
Are you playing sandbox?

No cordless mouse and I selected sandbox so I don’t know why this happens.

[editline]29th October 2014[/editline]

Actually sorry , no , where do I select sandbox?

On the bottom right of the main menu there is a box saying something (Name of a gamemode), click that box and look for Sandbox.