1: If you mean how to put your game on the Playdate then make sure your Playdate is plugged in, then go to the Playdate icon in the bottom right of the Simulator and click on "Upload Game to Device" (or command+U)
2: When you upload your game to device there will be a default card that has the game name on a black background. To customize this check out the Designing for Playdate launcher section and the corresponding part in Inside Playdate
After your pdxinfo is set up (see the links in Mathio's answer), you can simply zip your .pdx file and distribute the zip. People can then easily sideload the game via their online Playdate account.