How to enable the approval flow for the seller?

StoreHippo allows admin to have full control of approving and rejecting sellers. Admin can manage the newly added sellers by setting the default status of the newly added sellers in Settings > Seller Settings section in StoreHippo admin panel. 
You can also approve the rejected sellers and vice versa.

Please refer to this article to get  more details on seller approval flow:
http://help.storehippo.com/topic/approving-or-rejecting-sellers