The question arose how to access 3rd-party IRs in Vienna Suite Convolution Reverb.
Actually it's very easy: First of all, copy the IRs to any location that's convenient.
As soon as you have opened the GUI of the Convolution Reverb, click on the pulldown-bar below the label IMPULSE (1):
A file dialog window will open. Browse to the disk location where you have saved the IRs to and open any of the valid files.
After you have loaded the first IR, you will be able to scroll through _all_ valid IRs from this folder, simply by using the up/down arrows on the right of the pulldown bar (2). - Allow for a few seconds of loading time.
It's a good idea to save one (most likely the first) entry of a folder containg IRs as a User Preset (3). This way you will be able to access this folder directly (4) when you want to use Vienna Suite Convolution Reverb again later. - Look at it as some kind of bookmark :-)
... when you plan to use the plugin in an AUX-channel, it might be advisable to make this "bookmark preset" full wet before saving it (see screenshot). This will make the handling even faster.
HTH,