A Long Rest can be used out of combat to recover all HP, Spells and Actions.
In order to take a Long Rest, you can either select Long Rest from the radial wheel (same place you select the character sheet), and head to camp, or go to camp directly. You can interact with the Bedrolls or campfire to finish the current day, initiating the long rest. Simple’s do this 4 times.
Note that to take a Long Rest you need to have some camp Supplies (either food or Camp Supplies).