Depends on which MOBILE HOTSPOT your're talking about. There's the hotspot on your phone and there's an actual Mobile hostpot device you can take anywhere. If its for your phone, you have 1 of 2 ways to add the money for the hotspot. It basically has to do with the plan your set up on. If yo have a grandfathered plan (i.e. the $40/ shrinkage plan) yo can add $5 for 1GB of hotspot or $10 for 2GB (as long as the phone is hotpot capable)... If your plan has hotspot included, it runs off of and/or situation. For instance if you have the NEW $45 5GB data plan, hotspot is included and you can use the 5GB for browsing and hospot. However, if you've used up all 5GB for browsing, you won't have any data left for the Hotspot. For this, yo can add $10 data pack for an extra 2GB of data for the hotspot. NOW, if you have the actual Hotspot device, when you activated the Hotspot, you were given a mobile number (if you don't know the number, can tap the power on the device and it should give you the number.) you will have to call Customer Care to add the cards to that account and have them Restart your hotspot plan for you since its no way for you to do it yourself
You can sign into my account and click reboost. Or you can go to this page https://myaccount.boostmobile.com/primary/guest-replenish and add money without siging into my account. Reboost means add money to your account.