How to create an attachment record in Salesforce?

Create an Attachment
If your form contains a file upload field, you can attach the uploaded files to most Salesforce objects by creating a dependent Attachment object.
Create the parent object for the Attachment object.
Click the Add an Object dependent on button, and select the Attachment object from the list.
You’ll need to map the ID of the parent object to the Attachment object’s Parent ID. To do this, map the Parent ID in the field mapping section. Note that this is a required field.
The other required fields for the Attachment object, “File Name” and “Body,” will also appear in the Field Mapping section. You will need to map both of these fields to the file upload field in your form.
If you are running into difficulty opening attachments in Salesforce, try mapping your Salesforce Attachment FileType field to the Upload Field in your form as well.