To extract 7zip files, you need to
Download 7zip to extract it.
After that, the guide seems to explains it well.
EDIT :
First, make sure Antivirus is off by the time you prepares to download JNGP. A Must for Kaspersky.
Second, download 7zip and JNGP files.
Third, extract the files with 7zip.
Fourth, JNGP is ready for use, make sure to execute WE bat the first time JNGP is used. Next time you use it, use NewGen WE. It's a great thing to make a shortcut for NewGen WE
Make sure that JNGP is in whitelist of your Antivirus, for Kaspersky case, make sure it's off whenever JNGP is being downloaded and about to be executed (turn it off before opening JNGP and restore it back after you exit).
Hope it helps.