how do u mirror a mesh ?

hi im using blender 2.34 and wondering how to mirror a mesh. i tried the mirror thing from http://ashsid.szm.sk/mirror_eng.htm but i can’t do “M” for mirroring. any help ?

To mirror in Object Mode, use Ctrl-M. To mirror in Edit Mode, use just M.

…Or use the script provided on that site.

ctrl-m