Did you know that you evaluate information sources on a daily basis? It's true. You're also really good at it. Don't believe me? Well, let's stop and think about this for a moment and run through a few scenarios:
In Scenario 1, you likely chose the mechanic, but how often do you stop and ask yourself why? Why the mechanic over the local librarian? You likely chose the mechanic because: the mechanic does this as his/her job and does these kinds of repairs daily (thereby inferring that they have experience doing this). You also very likely have vetted your mechanic through past personal experiences and/or through recommendations from friends or family--because you don't just want the work done, you want the work done well.
In Scenario 2, you likely chose the advice of a close friend. Why? Because you have a relationship with this friend versus a complete stranger. You likely value your friend's opinion and trust their judgement based on what you know about your friend and what your friend knows about you. They know what you like and what you don't like, what you feel comfortable in, favorite colors, etc.
In both scenarios, you, the user, have a research question and need information sources to assist in answering the question. Once you find some information sources, you then evaluate their credibility to see, which best serves your research question needs.
See, I told you! You evaluate sources on a daily basis! We may not use this kind of specialized language, though, because, well...frankly it'd be a little weird, right? My doctor would probably think it's a bit strange if I said, "Hello, information source! I have evaluated your credibility and found that you are the best information source to answer my query." But, it doesn't seem as strange to tell a friend or family member, "Wow! I think Dr. Soandso is wonderful. Based on my experiences she always takes the time to listen, has helped me in my various illnesses, and just a pleasure to be around. Unlike Dr. Whatshisname, who always rushed me through a visit and never listened to my concerns, Dr. Soandso is a great fit for me!"
What I did there in the above example, was evaluate an information source based on criteria that I value. Each time you make a decision you are making some sort of evaluative decision based on the criteria you value to choose what information (or options) are best for your specific need at the time.
I say all of this because I want to help ground and normalize the research experience and illustrate that you do this regularly. You may not have as much experience applying it to Internet searching, but you are no stranger to evaluating sources!