After the battle with Brendan/May, return southward to Oldale Town.
Continue south and out of town, healing up if needed (though how that would be a necessity without obscene grinding, I don’t know).
Continue further southward back to Littleroot. Remember, you can jump over brown, raised ledges - much like other Pokémon games - but remember that it is a one-way deal.
Head south and into Birch’s lab. As you enter, Birch will call you over and decide that you should be given a Pokédex . As he explains, the Pokédex is a technological wonder that allows you to collect data on any Pokémon you can find: 721 species to date!
May will then also give you ten Poké Balls ! Poké Balls are capsule-like devices which hold Pokémon; you can use them to also catch Pokémon and then be able to train them at will.
With this event, your journey begins proper; it is now time for you to arbitrarily act on your unspoken goal of conquering the eight Gyms of the Hoenn region and then the Pokémon League.
Once you leave the lab, go north to Route 101 though as you approach, your mother will call. After the brief, sentimental scene, continue onto the route.
If you want to, you can use the Poké Balls you recently earned to catch Pokémon on this Route. Right now, there’s not much of note - neither here or Route 103, just Zigzagoon and Wurmple. Zigzagoon can be moderately useful as an HM slave, though.
In any case, as you enter the Route, May will come along and hand you the DexNav app for the PokéNav Plus on the Touch Screen, in turn letting you be able to see that you’ve caught (or not) certain Pokémon on a Route.
Additionally, as you go along the Route, May will also show you how to sneak up on Pokémon. Whenever you see a part of a Pokémon sprite sticking up out of the grass, you can move the Circle Pad slowly to walk to it and battle it; these Pokémon are usually special in some way.
For example, when you enter this battle, the Poochyena will have one of the elemental Fang moves, based on your starter - Ice Fang if Torchic, Fire Fang if Mudkip, and Thunder Fang if Treecko.
This will be your first occasion to actually catch a Pokémon, too. The summation will be to lower your foe’s HP as much as possible and then use a Poké Ball. If you need more detailed guidance and tips, check the Pokemon Capture section of the guide. Once that is done, continue into Oldale.
Heal up in the Pokémon Center to begin with. If you wish, you can buy additional Poké Balls and Potions in the Poké Mart, and they also now sell Antidotes.
For now, it’ll be best to just buy a couple of Antidotes; you have enough of the rest most likely to get you by to the next few towns. In any case, once you’re done, go west onto Route 102 .