You will need the Full Read Service Plans permission or be an organizer on the plan to perform this action.
Navigate to the service plan and choose "Download plan" from the Actions menu in the upper right.
A pop up will appear with options for the download. Make sure "Order of Service" is chosen for the Report field.
You can then choose which service times and fields to include in the generated output. You can include as much or as little information as required.
Once you've made you selections, click on the "Download" button to generate and download the file.