how do i

@MadisonsSim  The short answer is, any mod hosted at NRaas is safe, and there are other creators whose work has been extensively tested and demonstrated to work as intended.  The best way to sort them is to ask for recommendations on a site like NRaas or Mod the Sims, where there are a number of people who could give you a better idea of what's out there.

The long answer is, there are a few different reasons mods might not be safe.  One is the obvious: the downloads themselves might not be safe.  That's not a problem on well-known sites (NRaas, Mod the Sims, and Sims Asylum for example), but it's never a good idea to download mods from a random third-party site without doing your homework first.  Another reason a mod might not be safe is if it's outdated and doesn't work on your patch level.  Always check the download page to see whether a given mod is compatible with patch 1.67/1.69.

The third reason a mod might not be safe is if it's not well-made, as in, it introduces or changes data that could end up corrupting your saves.  That's when asking questions is especially important.  But like I said, there are sites where you can get information on any mods you might be considering, or ask which mods would help you accomplish whatever you want to do in-game.