A sprint (iteration) is a fixed period, usually from 1 week to a month. Before the sprint planning, you must have the backlog updated: all priority and current issues must be moved to the beginning of the backlog.

Before creating a sprint, you need to decide on a business goal: what you want to achieve within the sprint framework, what value you want to provide to the client. Depending on the goal, you will select the issues from the backlog that allow you to achieve it. Defining a goal is also important so that the team can concentrate on it and not to lose focus.

To add a sprint, click on the Create issue button or on the "+" in the backlog menu.

Specify the name, goal, term dates:

It is important not to set a too long period for the sprint. The shorter the sprint, the better the team will feel the timing and maintain a fast pace of work.

Now, you can start sprint planning.