This is text with 6 gaps in it. Each gap needs to be filled by a paragraph or long sentence that is missing. This can be pretty difficult, but what we are testing here is textual structure, so make sure you know how different types of texts fit together.
So look at the words and context. There needs to be logical continuation (flow) to the text. Look for words that refer to other parts of the text (small words like this/that/those/these/so/it/were etc).
Have a look at the following video on how to approach this reading task.