Hi @dianahchu
Here’s the [https://elektrotanya.com/yamaha_p-115b_p-115wh_p-45b.pdf/download.html|service manual] for a Yamaha P45B, hopefully it is close enough to a P45 to be of some help.
To download the file click on the “I am not a robot” checkbox below the document preview, pass the security check and then select Go to download. Be patient it takes a little while to find the file.
When you have the manual go to p.18 to view the dis-assembly instructions.