If you've uploaded your VHD you should be able to create a new disk using Virtual Machines > Disks > Create Disk
this will prompt you for the url of the VHD you uploaded and allow you to specify the OS type and a name for the disk.
From there you can create a new Virtual Machine. New > Compute > Virtual Machine > From Gallery > My Disks
EDIT
I'm told by a colleague that some storage accounts do not support disks for VM's and a workaround can be to create a new VM using the portal (either from scratch or using a pre-made gallery image) this will create a storage account called something like portalvhdxxxxxxxx. You should then be able to upload your VHD to this storage account and create your disk from there.