1. First, on the questionnaire editing page, find the form page where you need to add handwritten signature.

2. Secondly, click the place where you need to add handwritten signature in the form page, and select "Add Picture" or "Add File".

3. Then, in the "Upload Picture" or "Upload File" window that pops up, select a hand-signed picture and upload it to the server.

4. After uploading the picture, you can adjust and cut the picture to make it suitable for display in the form page.

5. Finally, save and preview the form page, and confirm that the handwritten signature has been successfully added to the form page.