One of the best places for information about finding, downloading, installing and caring for Mods and CC are fan sites like Carls Sims 4 Guide and Simscommunity. Both sites (you will need to scroll through articles in simscommuniy to find) have good basic instructions and suggestions for Mods and CC. Some Mod creators also have instructions for downloading and installing their Mods. Deaderpool for example has instructions for installing MCCC on his tumbler and has a discord for questions.
Can you ask your You Tuber about her Mods? She may have a blog or such where it is easier to ask questions (I don't watch You Tubers much so I'm less help with this).