Silicone sealant is fine but clear and blue are near worthless. Weak. Use black. Apply one glob each 120 volt power terminal, wait one day then go back for the second glob. First, check the clearance of the terminal board with the flapper orange lid closed. Then you'll know how high you can glob the silicone sealant. TAPE THE FLAPPER KID UP when silicone is applied while waiting to cure.
Black silicone is tougher than a person might think. Also silicone the positive and negative 12 volt wires and terminals. This acts as a strain relief. Dribble sealant onto the wire insulation as well. Might as well do it right.
If the copper wires in the jumper cables do not fit under the terminal tabs, split the stranding in half with your fingers, twirl each bunch, then fit alongside each screw. With larger cables I have had to strip enough insulation to make 4 strands then use 2 screw terminals each polarity.
On the side of the MEGAWATT there will be a slide switch. I have never seen one arrive set in the "220 volt" position but do yourself a favor and check this.
Be prepared to be PATIENT when twiddling the blue plastic adjustment pot to the left of the terminal connector row. It is insanely sensitive. You need to noodge fine adjustments. I had to re-twiddle a dozen times to arrive at a single wanted voltage setting. Do not force the turns beyond the stop. The adjustment pot is a three cent item and fully worth one-tenth that.
