how can I set my IPAD not to connect to internet from my computer??

You have an ad-hoc wireless network created with your computer that is serving as a wireless router for your iPad and other wireless devices?

Turn the router off. Or block the MAC address of the iPad in the router settings.

If your wireless network is password protected, select the network on your iPad to view the wireless network settings followed by selecting Forget This Network to remove the network from your iPad. Don't give the password to your network to anyone else that uses the iPad and don't join the network yourself. If your wireless network is not password protected, you should do so for a number of reasons.

Or you can make use of MAC address filtering with your wireless network and router - entering the MAC address for each computer and device that can connect to your wireless network and not add the MAC address for your iPad to the approved list.

Or, change the wifi security pass phrase on the router and don't put that pass phrase into the iPad.