If you are playing through from the beginning, you would need to do the log fetch quest and then go to the town to the left where you unlock a double jump. That allows you to make it over the gap to progress to the rest of the game's levels.
But you can also just skip all that and fast travel to any level in the world map by selecting various options in the "Skip to" menu at the start of the game. You can download the GBC ROM or if you're playing in browser, just refresh the page to reset the game and return to the skip menu.