Before you can assign work items to a sprint (or an iteration) in Azure DevOps, someone needs to create those sprints. That boring task is a great candidate for delegation. Unfortunately, the only role that can do this work by default is the project administrator. Before you turn everyone into a project administrator, let me show you a much more granular way to achieve the same goal.
Open the Project Settings, go to the project configuration in the Boards section and select the top entry in the iteration list. In the appearing three dots you find a context menu:
Click on the Security entry to open the permissions dialog for the iterations:
Here you can select roles or individual users and grant them the permissions to work with the iteration list. You need to give them the “Create child nodes” permission so that they can create the new iterations.
The change of permissions should take effect immediately.