On the dashboard you will find the image you uploaded on “Images & Snapshots” under your private images. Click on the Launch button and:
Select “Boot from image (creates a new volume).” as the instance boot source.
Ensure the device size is at least the same size as the image uploaded.
If you are importing an existing virtual machine, for its first boot you should choose a flavor that provides at least the same amount of CPU and RAM as the VM had before. Once you confirm the compute instance is booting appropriately, you can resize it to a smaller flavor if you wish.
Remember that your VM has been imported exactly as it was before, therefore there might be some things that may prevent you from connecting to it remotely (for example: a host base firewall blocking connections). You can use the console and your existing user credentials to connect to your compute instance and make adjustments to its configuration as required.