To change your Windows Server's RDP access password within the Windows OS, you need to follow these simple steps:

1. Press the CTRL+ALT+END keys simultaneously on your keyboard.
2. Click on the "Change a password" option.
3. Type in your old password and then your desired new password. Confirm your new password by typing it again in the confirmation field.
4. Finally, click on the right arrow labeled "Submit" to complete the resetting process/

If you want to change your server password from your control panel, you can do it. First, go to the "Your Active Servers" section of your control panel Dashboard and click "Manage". From there, navigate to the "Actions" section in the left sidebar and click "Change Server Password". Keep in mind that your new password must meet the Windows complexity password rules to be applied successfully on your server.

Once you have completed these steps, your Windows Server RDP access password will be successfully changed and you can use it to log in on the Remote Desktop application.