An example of a render:
An example of a stock:
How to render:
Pentool - Select your pentool > Ensure it's on path (can be editted on the top) > Trace around the lines of the thing you want to render > When you did it all around, right click > Make selection > Ctrl paste it into a new canvas.
Lasso tool - Find your polygonal lasso tool (it may be hidden under the regular lasso tool, just right click the lasso tool and select the polygonal) > Trace around the lines of the thing you want to render > Once it's done ctrl paste it into a new canvas.
The most popular ways to do it.
You can also use the eraser tool, but that won't be looking very good.