Prusa i3 build: questions about heated bed & thermistors.

Hey everyone! Newbie here.

I've got a few questions regarding Prusa i3 assembly that i'm hoping you might answer.


I am not sure how to solder the wires to the PCB heated bed.
I've got a 12V power supply. The PCB is a MK3 version.
Am I supposed to solder the negative (black) wire to both 2 and 3 at the same time? (See picture below)
Would it be possible to solder to just one of them? (If not, what is the reason for this?)
Attachment 6228
I am not sure how to connect the wires of the thermistors to the RAMPs board.
The wires don't have any female head to connect to the board's pins.
Should I try to solder the thermistor directly onto the board pins?
Or should I cut some Female Dupont cables (larger in diameter than the thermistor wires) from one end and solder these to the thermistor wire, then connect these to the board pins?

Thanks for the help.