This should look like you are attempting to install packages in requirements.txt but you write down the command. What you instead do is pip install -r requirements.txt
Explanation:
-r Option: The -r flag instructs pip that you're providing a requirements file. So it will figure out that it needs to step into a directory and check for contents of requirements.txt.
Path: Run that command in the same directory of where the requirements.txt has been dropped, or fully qualified Open terminal or command prompt. Navigate to the directory which you have your file, either open the directory where that is located OR use its path Paste this,
pip install -r requirements.txt