Very simply, I'm not sure how I get CC LR latest available version (5 or 6). I have a purchased version of LR 4 and am a new CC member. I installed LR and it is still 4. Should I uninstall my purchased version and reinstall CC to get LR 5 or 6? And do I need to do anything specific to ensure my previous presets and catalogs won't be affected?
If you are a new creative cloud subscriber then you should be able to download and install Lightroom CC from the creative cloud application manager. When you install Lightroom CC and then run it, it will prompt you to upgrade your existing catalog. This upgrade process will create a new copy of your catalog, leaving the original catalog intact and usable by the older versions of Lightroom.