You need to install Joonie's HFW 4.87 from the following post. Copy the file as PS3UPDAT.PUP in x:\PS3\UPDATE
https://www.psx-place.com/threads/4...n-4-84-4-85-4-86-fw.23094/page-95#post-267631
To install PUP you can do it from Recovery menu or from Settings > System Update.
You don't need Package Installer or homebrews to install HFW 4.87.
Once you install HFW 4.87, you're on an exploitable Official Firmware.
That means that you can to use it the same as OFW 4.87, but you will be able to install HEN when it is available on **ps3xploit.com >Domain no Longer owned by team** (ps3xploit.me =new)
EDIT:
If you can't wait for the official release, zecoxao reported in the following post the exploit works editing the javascript to force it to detect the firmware version as 4.86
https://www.psx-place.com/threads/new-version-4-87.31945/page-3#post-267715