Can I and how to install a bypass diode on a solar panel?
Use a Schottky diode and put it in reverse accross the solar panel normal output voltage.  You want the diode not to short out the solar panel in normal operation, but to provide a means to shunt current accross it when it is not producing its own voltage.

The problem is that solar cells are actually diodes with current going thru them in the reverse direction during normal operation.  But, this only works when there is enough light on the cell to produce the current.  When the cell is in the dark, think of it as basically a diode blocking the normal current flow.  When a bunch of cells are in series, just a single one in the dark, and therefore acting like a reverse diode in series, effectively blocks the current from all the others.  The Shottky diode in parallel with the cell but at opposite polarity allows the current from other cells to bypass a cell in the dark, minus the drop on the Schottky diode.