Some tips:
Finding CC:
There are some Tumblr accounts that reblog new CC. That's really helpful for avoiding old CC that might have been broken by game patches but never updated. Another way to avoid broken CC is to make sure you get CC from creators who are still actively making CC. You can check their Tumblr or Twitter accounts or their separate blog sites to see if they're active. If they haven't posted since, say, last November, a lot of their CC might be broken. (You can use my posts in the Mod section here to keep up with future breakage info.)
The sites mentioned above are reputable and don't repost creators' content without their consent.
Downloading CC:
You absolutely do not have to be a patron of a creator to download their content! Lots people never make their content patron-limited, and those that do are supposed to make it freely available after a few weeks at most. If they aren't doing this, avoid them -- you don't know which other rules they aren't playing by.
Installing CC:
To install CC, just drop the .package files in your Mods folder. If there's no .ts4script file, you can categorize the mods as much as four folders deep. A lot of people have a subfolder of Mods for each creator, as one approach.
If the file you download is a Zip or Rar file, extract the contents, put the contents in your Mods folder, and delete the Zip or Rar file.
Managing CC tagging:
If you find, like I do, that some creators' stuff doesn't show up in the categories you think it should, you can download the program Sims 4 Studio and retag it yourself! I do that a lot. Sometimes creators have accidentally tagged every swatch of their many different colours of a rug "blue," for example, or their straight hair is showing up under afro-textured, or they've tagged a dress that's knee-length as a "long" dress (I guess we have different ideas about what "long" is!), or they've tagged an outfit as "random" so tons of townies end up in it. Sims 4 Studio makes it super-easy to customize the tagging, and I can click through every swatch and delete the ones I'll never, ever use so that the files are smaller.