Within a lab report or scientific paper, the you place your abstract at the beginning of the report.
It is the first item after your heading, and just before the Introduction.
Abstracts for Posters and Presentations
Place your abstract near the top of a poster. We often put it on the title slide of a presentation. That way people can read it before the talk starts.
Remember why We Write Abstracts
It may have been a while since someone requested your article from the library or read about your presentation in the program for a conference. Put the abstract where they can read it again before looking at the rest of your information.