Install celtx on my new Ubuntu server

Hi,
I’m attempting to install celtx on my new Ubuntu server. When I try to run /celtx from the terminal I receive an error that says that the file libstdc++.so.5 can’t be found and libstdc++.so.6 is a more recent file version. To install a computer file that somebody has linked I tried using yum but yum has stated that it needs the celementtree.
I have tried to reinstall clementtree using synaptic but this has not worked. I urgently need to install celtx but also need to solve the issues I am having with celementtree and yum. Can someone help me?
Any help is most appreciated.
