With a tackle

Without hesitation, Charmy runs at Charmander.

When they both collide, Charmy finds his head buried into Charmander's gut for a split second. The inertia causes the charmander to flip over and bash his head onto the floor, rendering him ****.

"Aww man, I picked the wrong pokemon!" Blue raises his pokeball to return his defeated charmander. "Don't get too cocky, I will beat you! You'll see. I'll get a map from my sister and tell her not to give you one!"
"Red, Gramps, smell you later!"

After that horrible utterance of annoying garbage, Blue walks around you and exits the lab.

You lift up your pokeball and command your proud Charmy to return to his pokeball.

"Well now, this is a good start to your adventure!" Professor Oak says with a grin on his face. "I hope the rest of your journey goes well too!"

You place Charmy's pokeball into your pouch and walk outside with your very own pokemon.