To create an EBS Volume from an EBS Snapshot, click the Launch button from a Snapshot's homepage.
By default, the nickname of the volume will be identical to the name of the EBS Snapshot. Be sure to specify the availability zone where you want to create the new volume.
NOTE: You will not be able to change the volume's availability zone once it's been created.
If you leave the "Size in GB" field blank, the minimum file size that is need to create the volume will be used (1GB - 1TB).

Click the Create button.
A confirmation window will display some basic information about the new volume and also allow you to attach it to an instance.