After uploading them to the datastore, you can use the datastore browser in the vSphere Client to locate the .VMX file. Right-click it and choose the Add To Inventory option. VMware Converter can also be used, but might require some tweaking of the VM afterwards.
If I upload the machines that I'm using with VMWare Workstation 9 (but no with VMWare Workstation interface, with VMWare VSphere Client, browsing the Datastore and uploading the virtual machine folder to it), when I want to power on the virtual machine (after added with right click in .vmx file of the folder and "Add to Inventory" action), I'm receive an error message that tell me that the .vmdk file of the virtual machine not found (vmware esxi Cannot open the disk).
I'm think it is a permission problem, but I don't found the problem in any forum, :-S
thats not a permission problem - the vmdk formats are different.
Until ESXi 5.0 you could import those vmdks from WS with vmkfstools -i uploaded.vmdk esxicompatible.vmdk and then exchange the vmdk link in the vmx-file. With esxi5.1 you may need to load a module that can handle WS format manually
You can use vmware-vdiskmanager on the WS host to convert the existing vmdk into "monolithicFlat" format and then redefine that disk to esxi-compatible "vmfs" format - see my notes http://sanbarrow.com/vmdk-howtos.html#flattovmfs.
By the way - this topic comes up several times a week - you may have searched in the wrong area - look in the Converter section firstr