STEP 1 - Create your Membership Product on Shopify
Make sure you have a membership product on Shopify, or else please create one.

PRO TIP: When creating a new product on Shopify, make sure:
Product Status is set to ACTIVE
For Inventory, you have more than 0 quantity OR are not tracking quantity
Product has a price that is not $0
STEP 2 - Create Subscription on Ongoing
Create a subscription group with a plan and add the membership product.

Step 3 - Add Subscription Widget
From Ongoing, click Getting Started
Step #2 will tell you how to add the subscription widget to your specific theme.
Already created a subscription plan using Ongoing and now just need to connect it to the product?
Great, follow these instructions here.
How Do I Remove the "One-time Purchase" option from displaying?
Follow these instructions here.
How Do I Change the Text (such as "subscribe & save", "delivery every" or "subscription plans"?)
For 2.0 Shopify Themes, follow these instructions here .
If you don't have a 2.0 Shopify theme, click here.