In order to create and save different rate plans, follow the path
CALENDAR > MODIFY PERIOD.
Inside the window, follow these steps:
1) Select the period to be modified
2) Insert room prices
3) Select option Add/Save rule
4) Insert the name of the period (example: High season), then click Save
Image 1 - Click to zoom
Image 2 shows how to upload again the rate plan:
you will select it from the menu (1) so the prices will be uploaded automatically (2).
Image 2 - Click to zoom
Once the rate plan is saved, you will be able to upload again only prices.
You will have to insert manually the new period and its availability.