It's much easier to install your processor while the motherboard is outside of the case, as it gives you much more free space in which to work. First, you'll want to make sure that your CPU has either the supplied heatsink and or fan attached (which should have already been done by the OEM). Next, simply plug in your Processor to the CPU connector, usually located in the upper left hand corner of your Mainboard. Depending on what type of CPU you are installing, be it Slot 1, Slot A, or Socket 370, there is only one correct way to install the CPU, gently slide the CPU into position, and check to make sure you have it firmly in place.
Like the CPU, this should also be done whilst the Mainboard is out of the case. You should be able to find your RAM slots located in the upper right hand corner of your Mainboard. Most of today's mainboards contain 2-4 DIMM connectors, while some newer (and more expensive) Intel i820 based mainboards contain RIMM slots, RIMM memory modules are a faster (and MUCH more expensive) type of RAM compared to today's SDRAM DIMMs.
Installing the RAM sticks is a snap - literally. By using DIMM modules it does not matter what size (in Megabytes) they are, or where/what order you position them in. I find it best to install the first stick in bank0 (usually the one closest to the CPU) by gently aligning the golden connectors with the slot so that it fits in (don't worry there is only one it can go in, just like the CPU), apply some pressure, but don't force it in. Place any other sticks in succession there after, bank1, bank2 and so on. Installation is done in this sequence mainly to avoid any problems that your Mainboard may have to your first (or only) stick being in any other bank than bank0.