On the dashboard you will find the image you uploaded under the Images section. From here, you can either click on the Launch button next to your Image, or go to the Instances section and create a new instance.
Regardless of the method you use, once you reach the “Source” section of instance creation select “Boot from image (creates a new volume).” as the boot source. Then find your custom image from the list below (if you clicked launch straight from the image menu it should already be selected.) Also ensure the volume 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.