IF... you have a cache defined (single drive, pool of drives), AND your share you plan to upload it to is configured to use the cache, you would just upload it to the share and unRaid will handle the process of loading it into the cache and then actually moving it to the share later based on your schedule. As soon as the initial upload is completed, the file(s) will appear to be in the share and can be used as you see fit.
nitty gritty here: https://wiki.lime-technology.com/Cache_disk