Turn off the power and remove the
fixture. Then open the housing to
expose the ballast
Buy LEDs OnLine Converting Florescent Tubes to LED Tubes
Remove the ballast mounting screws.
Remove the ballast to a position which
makes the wiring assessable.
Cut the wires which lead to  the
connectors at either end of the fixture.
Organise the wires neatly toward the
connectors they go to.
Discard the ballast.
Strip 1/2 inch of the insulation from the
end of all the wires.
Remount the fixture and connect the
AC wires. Neutral to the connectors on
one side. Line to the other end.
You will notice that I used lamp cord to
make the power connections. You
should use wire recommended by code
to wire the fixture. I'm making this as a
demonstration unit.
Replace any covers you had to
remove to expose the now absent
ballast.
Insert the new LED Tubes into the
fixture making sure that the LEDs face
away from the fixture.
Turn on the power and enjoy a primary
lighting appliance which will outlast any
light ever made. Chances are that you
will have a reliable light for more than
10 years in a residential  setting. Their
life is not shortened by turning them off
and on many times a day and they last
10 years or more!