To address development problems in a draft, a writer generally needs to add material/content to the essay.
Sometimes this is required because the essay does not meet the word requirements of the assignment, but more generally an essay lacking development is too general: scenes are not described vividly, specific details are not presented as evidence.
To address development issues, you may need to make more observations or do more research, ask (and answer) more in-depth questions.
If you cannot find enough information to fully develop an idea, it may be because of poor topic choice (for example, to write a memoir, you must be able to remember clearly the events you were writing about), and if possible, you may want/need to think about starting fresh with a new topic.
Here are some links to material that can help you develop an essay.
Show, don’t (just) tell (Dennis Jerz)
Scene vs summary (This is particularly relevant for memoir assignment.)