Go to Configuration → Approval process → Add new approval process or edit the existing one:

Select employees that should be assigned to this approval flow:

You can define the type of approval: automatic or with specific steps. If the approval flow should go according to the approval steps, we need to define:

You can add one or several approval steps. In each step, you can assign one or multiple approvers. If a step includes more than one approver, all of them will receive a notification about the request; however, it is not required for everyone to approve it - approval from just one person in that group is sufficient.

The approver can be:

You can set up either one person or many employees as a multi-approval.

This option enables approving requests while the original approver is currently absent.
​

Here, you can choose who will be notified via email about the finally approved request. You can select a particular employee or the whole team to be notified.
​

You can define an alternative process with completely different approval settings. The alternative process is applicable only to a particular absence type.