I'm afraid you can't. Even if you buy SalesVideoCreator Agency without the Standard Version, you will not be able to login.
Here is why:
1. SalesVideoCreator Standard is the main product which is either an Yearly Subscription or Monthly Subscription.
2. SalesVideoCreator Agency is an Upgrade or Up-sell which adds the Agency features for your SalesVideoCreator Software.
3. Since SalesVideoCreator Agency is not independent, you will need to subscribe for the main product SalesVideoCreator yearly or monthly subscription first. Else you can't use the software by only having SalesVideoCreator Agency in your account.