im: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/im - from package: python-twisted-words

You may install the required package with command yum install {package}

Error in other languages:
im: bevel nie gevind nie
im: comandă negăsită
im: comando não encontrado
im: commande introuvable
im: command not found
im: käsku ei ole
im: không tìm thấy lệnh
im: komanda nerasta
im: Kommando nicht gefunden.
im: kommandot finns inte
im: komut yok
im: nie znaleziono polecenia
im: níor aimsíodh an t-ordú
im: no se encontró la orden
im: no s'ha trobat l'ordre
im: opdracht niet gevonden
im: parancs nem található
im: perintah tidak ditemukan
im: príkaz nenájdený
im: příkaz nenalezen
im: команда не найдена
im: командата не е открита
im: 命令找不到
im: コマンドが見つかりません