Press the Play button next to the game you want to play and select Pick Your Own Numbers. Tap the random pick (🔀) symbol in the upper right corner of your screen to randomly select all or some of your numbers for a given play using a random number generator.
If there is a number you really love, you can lock it in and choose the other numbers randomly. To do this, first select the number using the grid so that it appears on one of the balls at the top of the screen. Then hold down on that ball at the top of the screen. A small lock icon will appear on the bottom right corner of the ball. You can do this with one number or multiple numbers.
After you've locked in your numbers, press the shuffle icon on the top right to select the rest of your numbers randomly.
If there is a number you really hate, you can block that number so that it does not get included in your random picks. To do this, simply hold down on the number in the grid and a big red X will appear on top of the number. After you've blocked your numbers, press the shuffle icon on the top right to select the rest of your numbers randomly.