Redirect URl without www to URl with www

i would appreciate your help in advance
i tried so much to redirect my site from the address to

but it didn’t work for me.
i tried redirecting on htaccess, it didn’t help.

any advice? what can i do?

In htaccess you have to make redirect forcefully
form to

thank you for your help. i tried that it didn’t work.
maybe i’m writing it wrong.
can you that line here for me?