To manage the leaves, go to Attendance > Leave from the left side panel.
Click on the settings icon to go to the leave policy.

Now, go to "Leave Type". Click on "+ Add Leave Type" to add a leave type.

It can be casual leave, earned leave, sick leave, etc. You can add any custom leave type from here. Give it a name & choose a color. You can also add a description for that leave type. Click on the "Create Leave Type" button to set that leave type.

You can also edit or delete existing leave types using the edit/delete buttons on the right.