how to import from csv file to EntityForm
There doesn't seem to be any contributed module available for importing Entityform submissions from CSV.

You can simply try creating a small module which read CSV data and import Entityform submissions. To do this you can simply write a batch operation using Batch API and create Entityform Submissions using code snippet available here.

Another way could be to try Bundle Copy module that works with major entity in Drupal Core and also provide simple API for new/custom Entities. I've not tried Bundle Copy with Entities other than Node. You can try if this works with Entityform if not you can use its API and extend it.