1. Go to Maintenance > User 

2. Double click on the Signature box and select your Digital Signature image file

3. Click Save and Close 

4. Go to Sales  Sales Invoice > Task > Design

5. Highlight which format to add in Digital Signature and click Amend

6. Expand ‘SalesInv’  ‘Document Info’ 

7. Drag out [Signature] field into the format

8. Click on the tiny arrow on right top corner of the field 

9. Click on ‘Image URL’ […] and select your digital signature image file 

10. Click on ‘Sizing’ […] and select [Stretch Image] 

11. Click on File and click Save As

12. Key in your new Sales Invoice with Signature name and click [Save]

13. Now you can preview your Sales Invoice format with your own Digital Signature

Please refer attachment for the steps.

Thank you :)