How can I associate my prices to the field options?

Also, I am working on creating an order form for custom designs and I have a few drop downs and check boxes for different options and add-ons etc but i dont know how to associate a price to each option.  For instance if my customer selects a size of 5x7($100) and an upgrade of grommets($15) how do i associate prices with each option?  When those options are selected, how do i create a total and check out?  

Since Im using Shopify as my platform is there a way to send the payment to my shopify shopping cart for check out?

You can do it this way:

1. Add a calculation value for each of the options. Here's our guide on how you can do that: https://www.jotform.com/help/301-How-to-Assign-Calculation-Value.

2. Get the total by using our calculation widget. Here's how you can do that: https://www.jotform.com/help/259-How-to-perform-calculation-in-the-form.

Now, if you want to pass the final total the payment field, you have to configure your Payment field to get the amount from the calculation. Please check this guide to do that: https://www.jotform.com/help/275-How-to-pass-a-calculation-to-a-payment-field. 

As for passing the final total to Shopify's built-in cart/checkout system, I'm not sure if this is possible. Shopify allows you to modify the core files to include your own custom function, but I haven't done this before so I cannot tell. You may consider asking Shopify support about this matter.