Consistently making on-time payments is the biggest driver of credit score improvement. That's why your loan is designed to report 12 full months of on-time payments to the credit bureaus. If you pay off your loan early, you'll end up making fewer on-time payments and lessening the positive impact to your credit score.
That said, you are allowed to pay off your loan early or make principal payments ("principal payment" means that your payment will be allocated to the principal amount of the loan but not the outstanding interest) without penalties or fees.
You can make additional payments by calling our customer support team at 1-801-252-4427. Note that your additional payment can be set as an additional off-schedule payment or added to a currently scheduled payment.