OK. Once you've unzipped them, load Poser and load your V4. Then, go to File->Import->BVH motion. A dialog box will then appear where you can browse to the unzipped files and select the one you want to load. Another dialog box will appear, this time with a choice of selections. Leave them at the default, which should be 'Scale automatically' and 'Along X-axis' and click ok. You may get a dialog box about no matching part(s), just click ok to ignore it/them. The BVH file should now have loaded, and your figure should have moved position to match the first frame of the bvh. Your V4 may have disappeared from view depending on where the bvh starts the anim, just scale the camera or zoom out until you can se your figure again. Then click on the play button on the animation palette at the bottom of the screen t view the anim. Hopefully it wont be too bad, some bvh files can literally tie the figures up in knots! :)
Hope that helps.