Once on the page, the client will load (this may take a few moments as it downloads necessary assets). Choose a Username: Select a username to play.

For the "Full" experience, you may want to tweak the memory. In the launcher menu, look for a slider that says "Memory (MB)." Set it to 1024 (1GB) or 2048 (2GB). This prevents the "Out of Memory" crash when generating large worlds.

Disclaimer: Eaglercraft is a fan-made project and is not affiliated with Mojang or Microsoft.