I will assume you already have the iPad connected to Verizon's network and you signed up for the month to month service from the iPad itself.
In that case, the SIM you have cannot be used to add to your account. You will need to get a new SIM and get that SIM activated on your account. You can go to a Verizon corporate store and get this done or call customer service and they will send a new SIM out to you. You will then have your iPad on your More Everything account to share the total data for $10/month. There is no charge for the SIM from customer service of a corporate Verizon store. If you go to a Verizon Premium Retailer, this is a third part and they usually charge you for the SIM. If you go to the store, make sure you have your iPad with you. They will not just give you a SIM, you must have the device and get it activated on the spot.