How do I go about safely installing optifine/shaders?

I wanted to give shaders a try on my computer to see how it looks (I think I finally have a computer that might be able to handle them), but I’ve always been pretty hesitant downloading mods for minecraft or any other game, because I’m wary of malware and other possible risks.

I was just trying to do some research, and I found that there’s a site dedicated to listing bad sites that repost mods for either ad revenue or to distribute malware, which is great (stopmodreposts.org). But I kind of got lucky finding it because one of my google searches had a top hit for a site that shows up on that list. I actually found the bad site before I found the one warning me about it though, so I’m glad I found both before acting on anything at the bad one.

From what I’ve read, it’s either required or recommended to get optifine first, and then a shader pack. But while several shaders I found said they’re for 1.15.2, optifine.net only has one 1.15 version listed, and you have to unhide “preview versions” to even see it.

So, I feel like I’m missing something. And when multiple guides I’ve encountered have images of download pages showing Optifine 1.15.3 (which is fishy and makes no sense since the latest minecraft release is 1.15.2), it leaves me feeling unsettled about even trying to sort through all the proverbial bull crap to make it work and not have my computer contract AIDS.

TL;DR: can anyone experienced with safely installing shaders provide me the right links and any other important tips I may be missing?