Add states by clicking the 'add state' toolbar button.
Add connections by clicking on the connections button then the 'from' and 'to' states.
Change a state to be final by right clicking on it.

Use the bin tool to remove states (click on the state) or connections (click on the specific letter).

Follow the regular expression (target) and create diagrams to match the target.
Right click to toggle final state.

Left click on the letter of a connection to change the letter.

Kleene star ( * ) means you need to allow "zero or more" of whatever precedes the star in a regular expression.

For more complicated Finite Automata, you could build the parts separately then put them together.

The OR operator ( | ) means you have to allow for either letter to be chosen at this point in a word; so two connections with different letters coming from one state.

Sometimes more than one letter will precede Kleene Star. In this case, you must allow "zero or more" of the preceding pattern to be used in a word.