How do you use such in a sentence?

At its simplest it introduces an example:

"English Summer weekends are the time for many community events such as village fetes."

It can enhance an adjective and link it to a corresponding clause, for example:

"It was such bad weather the fete had to be cancelled."

Here, "such" stresses the "bad", suggesting prolonged heavy rain and wind, and hinting the corollary that a breeze and mere drizzle would not have stopped the event.