You have to configure your TDM card before using it. You should have a look at FreePBX documentation, I think there's some hints.
Basically, you'll have to configure your channels, this can be done with the command:
dahdi_genconf
Now, replace the context for trunks as dahdi__genconf put trunks channel in context from-pstn and FreePBX expect them in from-zaptel:
sed -i -e "s/from-pstn/from-zaptel/g" /etc/asterisk/dahdi-channels.conf
Now you need to configure your global chan_dahdi configuration: edit the file /etc/asterisk/chan_dahdi.conf and adapt it to your need, also, don't forget to include your dahdi channels configuration here (there should be a line like #include dahdi-channels.conf)
Then, you should comment each uneeded dahdi driver, for this, edit the file (it's not templatized) /etc/dahdi/modules and comment the driver you don't need.
Then /etc/init.d/dahdi restart
Now go in FreePBX interface and create a new trunk (type 'Zap'). The important part here is to enter the corresponding channel number. Then apply your change and test