Check with
apt-cache search pokerth
whether this package
http://packages.debian.org/sid/pokerth-server
is available to you.
If this is the case, it may be as simple as executing
aptitude install pokerth-server
or
apt-get install pokerth-server
from a terminal.
After that, you can execute
pokerth_server
(or pokerth-server, I'm not sure if the debian pkg renamed the binary)
To test if your server is running, start the pokerth client, go to Settings -> Configure PokerTH... -> Internet Game,
check the box Manual Server Configuration, make the Server address
localhost
Port = 7234
Then click OK, and in the start window try
Internet Game
If you end up in an empty lobby, you have connected to your own server.