These days securing your Wifi is essential, apart from a strong password a popular method is to disable the Broadcasting of SSID (Service Set Identifier). By disabling the broadcasting of the SSID it makes it harder for people to hack as they are less aware of it being there, the down side to this is if you change your device or the wifi password then trying to connect your own device to it can be a nightmare. thankfully there is a way on iOS devices but you will need to know the following: 

Step 1:
On your Home screen, tap settings 

 Step 2:
Tap the toggle switch to turn ON Wi-Fi. 

Step 3:
Tap your wireless network name (SSID)on the list of Wi-Fi networks and enter your wireless Password* (If your wireless network is not password protected, then tap your router’s wireless network name and your Android smartphone will automatically device to the network). 

*Passwords are case-sensitive. Tap the Show password check box to make sure you’re typing the password correctly. 

Your Android Device is now connected to your wireless network. You can now access the Internet.

Related
How to connect to a hidden network on iOS devices
How to connect to a hidden network on Windows PC