When working with files and attachments in Salesforce, we're dealing with binary data - the actual content of the files.
To add an attachment to a Salesforce object, we have to use the Salesforce action 'create object', and select the attachment object. we would need to obtain the binary data of the file we're working with. If you only have an URL to the file stored online, you can use our Utilities connector to read the file and retrieve its binary data. You can do this by inserting the URL into the "URL" field as seen below.
Subsequently, pass the binary data from the above step into the action. You could do this by inserting the "Body" data pill from the first step into your "Body" field that is required on the left under the Salesforce Attachment object to be created.