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On your Salesforce Account. Go To Setup -> Object Manager -> "FTP Attachments" Object.
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Click "New" in the Custom Fields and Relationships section of the page
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Choose the type of field as "Lookup Relationship" and click next
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Create a lookup relationship field in the FTP Attachments® object for ’YourObject’ with the name say ’YourObject’, because it is a custom filed Salesforce automatically appends "_c" to it at the end. Choose the object for which you want to enable FTP Attachments® , in our case it is ‘YourObject’
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Finish the creation of this custom field. Once done use the Custom Link Manage to create custom links for this custom object
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After creating link button add it to the page layout of the custom object
Now, you are ready to use FTP Attachments® with that custom object.