Along with Redhatterb's advice you need to cook them until tender. Allow them to cool and store in a freezer container with as much air removed as possible.
Google the topic to find the directions. No matter what you do with beets, you have to scrub them and cook them with the skins on them, and leave two-three inches of stem on them, or else they will bleed the color out, and they won't be the nice deep color that they normally are.
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