Open Jira project or any Jira issue,
Click the Approval Path button in the left menu,
Go to the Definitions tab,
Click the Add definition button.
A new Approval Path form opens. You can add a step or a parallel group.
The Approval Path Name is required. It is important because later you can start an Approval Path from a list of created definitions.
Click the Add step button and choose the step type you require.
More detailed information about step types.
To create a parallel group click Add parallel group button. Drop step/steps in the marked area.