Successful writers are able to communicate their thoughts, feelings and attitudes about a topic in a way that meets the needs of a particular text-type and its audience.
For a literary writer such as John Steinbeck, his particular context was 1930s USA, a time of great poverty and abuse of power. This context brought him to write the novel Of Mice and Men.
The key to putting context to use is to find ways to imagine yourself in the situation of a real-world writer. For example:
if you are asked to write a letter of complaint ‘become’ the person who feels angry enough to want to complain
if you are asked to write a leaflet promoting a zoo ‘become’ the advertising agency writer whose job this would have been