to install RAM in matching pairs, with identical timings, from the same manufacturer.
If you buy a matching pair, it will be automatically configured as dual channel, start out with 'middle-of the-road', as sometimes when you try to pop in the fastest RAM, the problem of BSOD will appear (usually this is dealt with a few tweaks in the BIOS, but if you don't have to 'tweak' something, then don't).
Either way, you'll still have to probably upgrade the BIOS, as motherboards don't usually ship with the latest BIOS settings.

Hope this helps, and good luck with your build Happy