NOTE: It's important that you only adjust the fulfillment type of your Amazon listing in Sellbrite. Do not make fulfillment type changes directly in your Amazon account. Doing so can cause ghost listings.
There's three different ways that you can change the fulfillment type of your Amazon listings: Manually, in bulk, or by using an Amazon Offer Template.
You can manually change a listing's fulfillment type by simply opening a listing page and clicking on the "Offer" tab.
Under "Listing Details" you will find the "Fulfilled By" field. Click on the dropdown to select either FBA or FBM. Now simply click "Save & Publish" and you're all done!
To change your fulfillment type in bulk, navigate to the Amazon listings page and select the listings you would like to change the fulfillment type for. Once your listings are selected, click the "Bulk Edit" button and select the fulfillment type.
This will adjust the fulfillment type, but it won't automatically publish the changes to Amazon, so make sure that you publish your selected listings for these changes to be reflected in your listing on Amazon.
Lastly, you can use an Amazon Offer Template to adjust the fulfillment type of your listings. Navigate to Settings > Listing Templates & Recipes. Select Amazon and click on an existing Offer Template.
Click the "Fulfilled By" dropdown and select your fulfillment type. Save your Template and the changes will be reflected for ALL of the listings this template is applied to.