External hard disk on read-only

Hello everybody,

I have an external hard drive formatted on mac os extended and it shows read only, how can I change it to read and write?

Thanks in advance

Reformat it would be the simplest way. If you can't do that, "get info" on the drive (select the drive, press command-i) and then scroll to the very bottom of the info sheet, unlock the lock with your admin password, then check the box that says "ignore ownership on this volume."

I could NOT find the option "ignore ownership on this volume"