you need the Flute that wakes Pokemon up i forgot what it is called. to get it, i think u bring a certain apricorn to the guy who makes stuff out of them.. i hope i helped!
Flash can be found on Route 2 in Pokemon Yellow Version.
sleeping on route 12 (unless you already woke it)
In Yellow Version, Ponyta is found exclusively on Route 17; its encounter rate is 24%.
You could either trade from red/yellow version or I have heard rumors of videos that tell you about a glitch to catch him.
Route 13
Basically it's the 3 (and pikachu) beginning Pokemon you got to choose in red and blue version, you can get them from people in the game one is in cerulean city, the other on route 24 and the last in vermilion city.
In Pokemon Red/Blue/Yellow/Green/Fire Red/Leaf Green version a girl in Vermillion city will trade you one if you give her a Spearow. In Pokemon Diamond/Pearl version, it a swarm on Route 221.
Nest to route 5.
catch it on route 1.
Its on the Route west of Celadon city and east of Vermilion city.
In Route 3,4, and 23.
Poochyena is not found in Pokemon Black Version. It is found on Route 9 in Pokemon White Version, however.