I manually drew some shapes and grouped them. Then I was trying to put them on top of a text box and let the texts avoid those shapes by choosing Object→Arrange→Bring to Front and choosing Object→Text Wrap→Make. However the texts were still behind the shapes. I've searched for online solutions but nothing worked. Any thoughts?
Alright I found the answer to my own question. The reason was that the text and the image were not on the same layer. There are requirements for text-wrapping to happen: Text and object MUST be on the same layer. Text MUST be on top of object to be wrapped. Text MUST be area text.
To play with layers, here is a good guide: https://helpx.adobe.com/illustrator/using/layers.html