Go to your online store and add on the URL, after your store ID, a text "#develop-apps". This address will take you to a site, where you can add a new app and create the needed access tokens.
Create a new app and copy the secret token to myOGO.
Go to the myOGO "Edit merchant" page and click "Add" new integration.
Copy your shop ID and the secret token to the integration. Remember to enable scheduled latest changes updates.
Note that if the "Ignore products missing from OGOship" is enabled, the setting will ignore all the products missing from OGOship and will not add them to the orders. The safer option is to ignore certain products, e.g. if you want to send them yourself, ignore them one-by-one on the product sync page.
Read more about product sync page.