Here is two tutorials how to do this.
You have access to your VDS over SSH:
- Connect to your server over SSH using root
- Type command "passwd" (no quotes) and press enter
- Type your new password
- Confirm the password
- It is done.
You have not access to your VDS over SSH:
- Login to control panel
- Choose your server
- Type new password at field "New root password"
- Press button "change password". This will reboot your server and a new root password will be set and emailed to you.