You don't need to give "ALL FOLDERS" 777 permissions (assuming you changed the permissions of the content of the Elgg install directory). That's even a BIG MISTAKE because anyone is now able to write/delete these files and directories. On a local server this might be not critical if the server isn't accessible over the Internet and there are no other users with local accounts on the server. But on a public server this would the CRAZY. Best would be to restore the original permissions (or just delete the install folder and extract the Elgg zip archive again into the install folder).

The data directory should be outside the document root directory, i.e. should not be directly accessible by the webserver (or over the Internet). This data directory - that you need to create yourself - must be readable/accessible/writeable by the webserver. So, you can either give this data directory 777 permissions or change the user:group of this directory to the account the webserver runs as. When installing Elgg you need to provide the full path (on the filesystem) to this data directory.

and I did too, create the folder at the same level where you install elgg , ie outside publich_tml , giving 777 permissions , and yet it does not work . I wish you could tell me a little more detail. apology but I am a total newbie in elgg

thanks to everyone who helped me . I solve my problem , I was omitting information from the path , I thank you infinitel