는지 알리다

tell someone what, where or how

The -는지 clause is an embedded question — what content, where I bought it, how wrong you were — and 알리다 is letting someone know it. Every line here uses the giving form 알려주다/알려드리다 rather than bare 알리다, because the information is being handed to a listener: 어디서 샀는지 알려드릴까요? (shall I tell you where I bought it?), 어땠는지 알려주세요 (let me know how it was). Contrast -는지 알다, which is knowing the answer yourself rather than passing it on.

Register: neutral to polite; common in videos addressing viewers