These pages provide some more details on how to use our ICs (the data sheets should be your primary source), and for those that are not too experienced with building circuits we provide some help on the construction and testing of them.
If you are having trouble understanding how to build a particular circuit, then perhaps it would be best to begin with a smaller project and progress to where you are comfortable building larger ones. If you do not already have one, a solderless breadboard such as this is a very good investment:
It allows you to construct a circuit without having to solder the connections (and it’s quite easy to correct mistakes with it too). Perhaps a small circuit such as an ELM409 debounce IC with an LED to see the output change state is a good place to start. Use a 3V supply (two dry cells) to provide a safe level that is likely not going to damage anything if you do make a mistake.
Once you are ready to tackle a bigger circuit (such as an ELM327 OBD Interpreter), you are likely to have several questions. Your questions may well be answered in the Application Notes and circuit Construction Tips sections, so look there for help. If you are building an OBD circuit, there is information specific to them in the Help > OBD section.