Yes, you should download V4 via your DAZ account. There are generally different files for Poser and DAZ Studio,. (Even though they're all labeled DAZ Studio. Some kind of bug.) Make sure you get the right one.

You'll get to recognize Poser files from DS files. You don't want the files with "pwrloader" or "cfstudio" in them. Poser files are usually have the plainer names. They may have "ps" in them somewhere. Really old files will be executables, ending in .exe. Those are Poser files.