Hello Jo,
You do have to have the same (or newer)version of LabVIEW that the LLB is written in.
You can then click on Open VI from the LabVIEW Splash Page or with a VI already open you can go to File->Open and navigate to where your LLB is located on your hard drive. Once you select the LLB a dialog box will open showing all of the VIs in the LLB. Double click on the VI you want and it will open up for you.
I hope this helps out.
Doug