You can delete existing Virtual Machine by following below steps:
1) Login to VPS Web Management Panel.
2) Click On Virtual Private Servers - Refer 1.png
3) Click On 'x' icon beside virtual machine to be deleted - Refer 2.png
4) Select the check box to delete the virtual machine. At this time, please ensure that you've backed up any/all required data since everything will be wiped off. Once done, hit Delete Buttoon - Refer 3.png
5) Wait for some time for deletion process to complete - Refer 4.png