Power measurements for Arduino Uno

hi,
please detail with pin # or schematic how to take current/voltage draw from Arduino Uno, when being powered by battery. I have two multimeters.
thanks in advance.

The current measurement is the more useful (a battery has its own voltage and will control
it well). To measure current the multimeter leads must be plugged into the COMMON and
current-measuring sockets (many multimeters have a low current and a high current socket,
start with the low current one, marked "mA uA" or such, not the high current (typically "10A")

The multimeter leads go to the battery positive, and the +ve input to the Arduino, i.e. the
multimeter is in-line so that the current flows through it. Do NOT place the leads across
the two battery terminals when measuring current - the meter would short-circuit the battery.

What kind of battery?
If it is a battery pack, put a small strip of double sided PCB between two batteries then use a amp meter to complete the current path, measure the current.

thanks,
do you mean Ve+ Vin after ground pin?

3xAA Battery+ to meter+,
meter- to 5V on Uno header pin.
Battery- to Uno Gnd.
One big electrical loop, yes?

The meter acts as (or has) a very low value 'shunt' resistor that you have now wired in series with the positive supply.
examples dipmicro electronics
A small voltage is created across that resistor as current flows (good old Ohms Law, Voltage = Current x Resistance, or V=IR).
The meter measures that voltage, and does the math (V/R=I) to display on the screen.