Electronics newb here. I don't understand how to physically connect batteries.

I'm trying to use a SparkFun Muscle Sensor with an Arduino for my project. I don't know where to begin with to physically connect a power source to the muscle sensor.

Here is the User Manual for the SparkFun Muscle Sensor:

It shows how to power the Muscle Sensor using two 9V batteries. I was wondering if there was a way to bypass the 9V batteries and instead power it using my Arduino Uno. If so, which pins on the Muscle Sensor connect to which pins on the Uno? I would imagine I'd connect 5V to +Vs, Gnd to Gnd, but I don't know where on the Arduino I'd connect the -Vs pin to.

If I can't power it using the Arduino, can someone explain to me like I'm 5 years old how to physically connect two 9 V batteries to the Muscle Sensor? The User Manual gives me the instructions, but what else will I need in terms of materials to make the connection happen? HOW do I connect the - terminal of Battery 1 to the + terminal of battery 2, and THEN connect both of those to the Gnd of the Muscle Sensor? After doing that, HOW do I connect the remaining terminals on the batteries to +Vs and -Vs of the Muscle Sensor respectively?

Two of these, solder as per you image:
HERE

I think the this plug would work for the electrodes:
HERE

For Electrodes, something like these would work, may have to cut them down:
HERE

Thanks. I already have everything I need for the electrodes. My only problem is powering the Muscle Sensor. I have two 9 V batteries, but I do not have the 9V Snap Connectors. Furthermore, I still don't see how I would connect the 9V Snap connector that you linked to onto my Arduino Uno.

So is there really no way to get the power requirements I need for the Muscle Sensor board directly from the Arduino Uno instead of using an external battery?

Not from the UNO, you need a bipolar power supply using the two batteries.

If you have two old 9 volt batteries, you can salvage their connectors and solder + to - which becomes the common or Ground.

Then the free + terminal is your +9 V and the free - terminal is your -9V.

Only the two terminals you solder together goes to the Arduino ground (0v).
The +9, -9 and the two terminals (common or 0v/ground) go to your PCB top left corner of your image.
+Vs GND -Vs

The Arduino Uno is not a particularly good way to get power in general, since USB ports cap out at 500mA, and the regulator caps out not far above that if using DC power jack.

In any event, there is no way to get power for that device out of the Uno without at least one DC/DC converter. Look at the PDF - not only do you need +9v, you need -9v too! So with external 9v DC power, you'd still need a dc-dc converter to invert it to get the -9v (also, unlike normal stepup/stepdown converters, which are available assembled from everyone and their mom, ones that invert the output are less common)

What's the problem with just using the batteries, and connecting them like they show in that picture?