Here is a simple way I use the tool. (By the way, if you don't see the tool, click in the lower right hand corner of the lasso tool you will see three options, select polygonal lasso)
By selecting the tool and while on the layer you want to cut select the area you want to remove. Close the blinking lines and click delete on the keyboard. You can only make the blinking line go away by selecting the crop tool, and clicking on the canvas. Not sure why Adobe makes ya do that, kind of a waste of time, but that is how you make it go away!
This is the finished product, a cool Element (wired heart) that now appears to be wrapped under and over paper.
This tool is so helpful when you want to wrap ribbons, stitches, even paper in and through elements. Makes for a fast extraction tool when you want to remove anything from a photo *note, if you want to use it for that purpose you select the area you wanna keep then click on the top tool bar menu "select" and click "inverse" - then you can click delete*
Here I extracted my sweet baby Parker out of a photo, placed him on some paper that highlighted his expression, used some elements to wrap under and over. Would of taken me a long time to try and do this layout without the Polygonal Lasso Tool!
Have fun with this tool! It is a time saver and a creative inspirational tool!