how to instal dvb-t on tvheadend
First of all, you'll need a USB dvb-t SAT>IP receiver to connect on your pc.
There are many cheap USB sat-ip receivers around. Once you have installed your USB SAT>IP receiver (with all its associated drivers), you'll need to install the tvheadend server on Linux Ubuntu.
Here is a youtube tutorial:
In case your operative system is Windows, you can use DVBViewer, which would be - in my opinion - less complicated to set up.
Here is a youtube tutorial to install DVBViewer: