Building a biphenyl for a linear transit run

Select the 'benzene' structure and paste it into the drawing area 
Press control-h to add a hydrogen to the vacant site
Press space-bar to select the benzene again and double click on the hydrogen
  that was just added
Go to the Main Options and select the 'Linear Transit' preset

The linear transit preset will automatically set the coordinates to internal coordinates.

Go to the coordinates window
Select the phenyl group that was added in the second step

The second atom of the second phenyl group should define a dihedral between the two phenyl groups. You can test this by changing the value of this dihedral in the coordinates frame.

Now, we would like to set up a linear transit run which will twist the phenyl groups along this dihedral.

Select the carbon atom that defines the dihedral
Go to the 'Linear Transit' menu

Notice that the panel asks you to define the linear transit parameters and shows the coordinates corresponding to the selected atom. If you select other atoms, their internal coordinates will also be shown. But you already know that this is the correct one.

Define the dihedral as a linear transit parameter running from 0 to 180 degrees
Press the 'Add' button

Running this kind of calculation can take quite some time, so we won't do that.