This is a 7 function multmeter. To check a car battery you would move the dial
To the DCV setting at number 20. I think the battery should show 12? Down on the right
Hand corner there are three plugin outlets(See Attachment) do I put the positive in the first one
And the negative to the second one of the meter??

You plug the red into the positive, and the black into the negative. Have on a Higher scale than expected to prevent burying the needle if analog or out of range if digital.
The other plugins may be for current, this is used inline with a circuit, usually? 10 amps max?
You may read more than 12 volts.
Try reading the battey voltage before starting engine, take note of voltage, then start car and test voltage again to see a higher voltage and charging.
Be careful not to measure voltage on the resistance scale.
When set for resistance, hold probes together and Zero out if available, If not, touch probes together and you will read your leads resistance, subtract from your resistance reading.