A good way to add words to your story is to surprise your characters. It can be a pleasant surprise (i.e. the super actually fixed the plumbing in your main character's apartment), or an unpleasant surprise (i.e. despite sending payment for a bill on time, it arrived late... and now your main character owes a late fee, as well as the original bill).
In my opinion, unpleasant surprises are better. Not only are they more realistic and relatable, but they also take up more space on the page.
If you can link the unpleasant surprise to your main plot, that's great. If you can't, it will probably reveal a side of your main character that the reader hasn't witnessed yet.
The unpleasant surprise can be anything from a wrongfully-sent foreclosure notice to a change in a plan to attend a play/movie/event that the main character somehow misses. Either way, presenting this challenge will show your main character's:
A. creativity in succeeding despite the unpleasant surprise,
B. stubbornness as he or she refuses to change his or her plans, or
C. resignation as he or she decides to avoid the problem entirely.
See the writing prompt above for an example, and have fun writing!