To install, drop one of the two files from the archive into the CLEO folder inside the game folder. (If there is no such folder, then you need to install the CLEO library)
There are two files in the archive - one gives regeneration up to 100 units of life, the other up to 50 as in GTA 5. The regeneration rate is ~ 1 unit per second.
P.S. the script is not mine, someone else's ruled for himself. Thanks to the author of the script.