In many instances, essays may not state the overall conclusion in a clear way or, sometimes, may not state the conclusion (main claim) at all. If so, then you must construct the conclusion for yourself as best you can from the essay.
"Nuclear powerplants are hazardous to human life and the environment. Thus, these plants should no longer be built." The indicator word 'thus' at the beginning of the second sentence indicates the conclusion which is: these plants should no longer be built.
If no conclusion or main claim is stated, you can construct it by finding the main question which the essay directly addresses.
Create a heading labelled yes - Conclusion
Start the paragraph with.. The conclusion or To summarise or The aim of this essay paper has been to..
Summarised what you have stated in the essay in brief.