ShipStation doesn't have a store to purchase printers from, but we do partner with Stamps.com and periodically there is a promotion for new users to purchase a printer through the Stamps.com store at a discount. To access that discount you must receive an email with the promotional offering and access the store through the link in that email. This automatically applies the promotional discount to the purchase.
The email is sent from Stamps.com to the email address you used to set up your ShipStation account. It lets you know your USPS account that you receive for free with your ShipStation account is now active. I recommend doing a quick search in your inbox for emails from Stamps.com or for the phrase "your usps account is now active".
Here is a link to the hardware section of the Stamps online store, if you'd like to purchase a printer directly from there (no discount will be applied if you access the store directly, though).
Hope this helps!