I am not sure that I understand your question.
Sometimes people have trouble choosing a new peak if there is not already a detected peak whose boundaries they can adjust with the mouse.
If you want to specify a brand new peak on the chromatogram graph, the way to do that is to point the mouse below the X-axis, and click and drag horizontally below the X-axis to specify the start and end points of the peak.
It sounds like you were asking something else.
Can you send us your Skyline document?
In Skyline you can use the menu item:
File > Share
to create a .zip file containing your Skyline document and supporting files including extracted chromatograms.
If that .zip file is less than 50MB you can attach it to this support request. You can upload larger files here:
https://skyline.ms/files.url
-- Nick