Otherwise, you won't know what to enter into software. There are some great beginners books to start off.
Also worth (after you've learned some minimal basics) trying out projects from books or the web, and then changing them slightly and seeing what happens.
If you're already familiar with electronics, are you asking how to run simulations with software, or how to create circuit boards? Both of those topics require knowing the basics.
Fair warning: a simulator will not software design a circuit. Even the simple simulators are not trivial to understand, if you don't have the theoretical baggage.
Fair warning: a simulator will not software design a circuit.
Sometimes they do. The major chip companies usually have tools for designing and simulating active filters and dc-dc power supplies. Here are some examples:
