Tap the arrow next to "Select Type" and choose "Guest."
Name your network, choose a password, and make sure "Isolation" (the main security feature) is on by default.
Under the "Duration" section, choose how long the network will remain active. Select "Endless" to keep the network on until you delete it, or select "Custom" to set a date and time for the network to become active, as well as a date and time for the network to delete itself.
Tap "Save" to finish setting up the network.