The process for listing a Variation Listing is the same as listing a non-Variation listing for all storefronts except Jet. Click here for Jet Specific Instructions.
Navigate to Listings > Listing Management > Unlisted Products Tab > Select the storefront you would like to list on from the dropdown > select the parent product and click 'Create Draft' You can edit UPC and variation price while the listing is in "Draft" status. You can find an overview of draft listings here.
To move the listing from "Draft" to "Active", Navigate to Listings > Draft Listings > Select the Parent Product and 'Publish'. Note: You can edit UPC and price for each variant while the listing is in Draft status.
Note, listing the Parent Product will create a listing containing all of the variants. The individual variants can also be listed individually outside of the variation listing by listing the child skus individually.