To access the Squid settings, go to the Squid main screen (landing page), tap the three horizontal lines in the upper left to open the app drawer, then tap the gear icon in the top right.
From device settings
On Android 7+ you can also access the Squid settings from the device's application settings. To do this, open your device's settings, tap Apps (or Applications or Application Manager) then tap Squid. On this screen, look for a gear icon or an option like "In-app settings" or "Additional settings in the app". This may be hidden under an "Advanced" section.