How can I hide other wifi networks so that they don't show up when I click on the wifi icon?

All WiFi networks that you have configured in WiFi settings - that are detected and within range of your iPad - will appear in the My Networks list of available networks.

The WiFi networks cannot be hidden, but can be forgotten whilst they appear in the My Networks list. Tap the corresponding blue “i” icon, then tap Forget This Network. Note however that whilst the WiFi network can be removed from the My Networks list, the WiFi network will still appear in the Other Networks list.

Sorry, not possible. You will always see WiFi networks that are within range of your iPad.