I saw the datasheet of your DPM. It can accept a max. 200mV DC. So to measure 10A DC you should pass your current through a shunt resistor such that it will drop 200mV across it when 10A current is passed through it. Here 200mV is the full scale. But you can also choose any other value say 10mV or 100mV(Easy to read) and calculate your resistor value as shown.
So the value of resistor will be
R=V/I
R=10mV/10A
R=0.001 Ohms
The power dissipated will be I*I*R=10*10*0.001=0.1 Watts
The power dissipating capacity of resistor should be more than 0.1W for safety. 0.5W is ok.
Use this resistor in series with your power supply's positive rail and the two ends of the resistor will be your input lines to DPM.
If the resistor value is difficult to get use full scale range of 100mV and calculate the resistor value accordingly. I have chosen 10mV as fullscale because the LCD reading will be directly in amperes and you'll not need to do any calculations.
Hint: You can also use resistors in parallel to get the desired value.