Once you have searched for your prescription, the results page lists pharmacies and prices in the ZIP code or city specified. Above the list are the four dropdown menus to further narrow results so you find exactly the right Rx deal for you. These allow users to select branded or generic medication, specify the form (tablet, liquid, capsule etc), dosage (10mg or 100mg) and quantity.
Here is a picture of the drug options menus:
Simply adjust these to find the right deal for you and prices will reload automatically to return the remaining vouchers matching your prescription needs.
Once you have found a voucher, just take it to the pharmacy and give it to the pharmacist. If you need more help read more here: https://help.rxspark.com/help-for-patients/how-do-rxspark-vouchers-work.