You can click the "Running" check box to stop it long enough to enter your own pattern. Then check the "Running" box again to resume "life".

Select an item from the menu and click the board to paste it. The item's upper left corner will align with the position of the mouse click.

The "Clear" checkbox stops growth and clears the board.

A simple blinker:

 A more interesting blinker: This one grows to be a big blinker A glider, moves slowly down and to the right. A mirror image will move down and to the left: Spaceship: move straight across to the right. A mirror image will move straight across to the left.

Here are some life related links I've found:

Wonders of Math - The Game of Life
Conway's Game of Life: an Overview
Game of life code in Java

You can find more by searching on "Conway's Life" or "glider gun"