There are tons of websites and books covering C, so I would just start with one.
For recommendations you may search on amazons top list with focus on C programming language where you will get many reviews and ratings on available books.
For a reference book on C++ I use often
this one (you may also take a look at Programming: Principles and Practice Using C++).
Although I haven't read one of the " ... for dummies"-books I heard that they could be recommended to beginners.
I would start with a book rather than just relying on online resources at the beginning as you have something you can work through from beginning to end.