I installed new battery on vehicle. Then turned the ignition over several times, only clicked. A small ground wire attached to the top of the motor became hot enough to melt the insulation on the wire.
Sounds like you need a better ground wire and a replacement starter.
First thing would be to replace the burnt wire with a heavier gauge wire. Then check your connections at the battery for being loose and or corroded. Clean them well, both the cable end and the battery terminal. Then check the connections at the stater and clean them making sure they have good contact and are not saturated with oil.
A rule of thumb
One hard click is a sign of a faulty starter. Several clicks (click, click , click, click) indicates a weak/dead battery.
