[Koha] Trouble Installing Koha

[Leila Ammar]

Hello all,
 I am trying to install koha (and use Linux) for the first time and am
  not very Linux savvy at all I   am afraid. I am having issues  with
  installing idzebra  but keep getting error messages regarding missing
  dependency libyaz3 which won't install because I keep getting this
  error message
   >> Depends: libgnutls13 (>=1.4.0-0) but it is not installable
  >> Depends: libicu36 but it is not installable
  Can anyone tell me what I am doing wrong and how to fix it?
  Thanks
  Leila