Schematic capture (drawing schematics with software) and PCB layout are non-trivial and require a certain amount of dedication to learning the basics.
Typically you start with a schematic so the software can help you make sure the PCB is correct. You *can* go to the PCB layout and just start drawing traces and such, but that is very error prone and a lot harder IMO (although some people do exactly that).
Probably one of the hardest parts of schematic capture and PCB design is getting the components you want to use into the software. A component usually consists of two main "parts", one is the symbol and pin detail used in the schematic. The other is the footprint used by the PCB layout, which is the exact size and shape of the holes or pads that the part will be soldered to.
Many EDA (electronic design automation) software come with hundreds of thousands of components with symbols and footprints ready to go. However, no matter how many parts a software claims to have in their libraries, I find that many of the parts I need are not available. In that case, most software will provide you the tools to make your own components, i.e. draw the symbol, specify the pins, draw the footprint, and associate the symbol the the footprint. You get the component details for the manufacturer datasheet, which will include the physical dimensions for the footprint pads, holes, spacing, thermal requirements, etc.
You will find that chips, edge connectors, etc. are almost always based on standard sizing, i.e. through-hole DIP chips will have a 0.1" pin spacing, same with standard headers, etc. Surface mount components are usually metric and have a 1.0mm pin spacing, or 0.5mm for fine-pitch parts, etc. Again, check the datasheet.
For the board-edge connections on the 99/4A, you are looking at 0.1" spacing, but you need to check the datasheet of the edge-connectors for recommended widths of the copper edge-pins.
I don't recommend KiCAD for a beginner. Yes it is open-source, but how tall and thick of a brick wall do you want to beat your head against? If you plan to make your design open source itself, then go with something like CircuitMaker or EagleCAD hobby version (both free). CircuitMaker is the free version of industry-leading EDA software publisher Altium, and is pretty awesome IMO, especially the routing features. This is *NOT* a stripped down version of their flagship software. You get full access to the software as long as you are willing to keep your designs open source.
Oh, and don't auto-route. Manually routing a PCB is not that hard, however, making a good (and working) PCB is an art as much as science.
Plan to spend some time learning the lingo and basics. Find some tutorials and follow them to get and understanding of what all the parts are and how everything fits together. There are video tutorials for both CircuitMaker and EagleCAD for beginners that take you through the whole process.