photoshop 2

Last time, i wrote instructions on how to make a hollow circle. I knew this but I didn't know how to make thick, curved lines

to do this, you use the pen tool, tap on one spot and then hold your mouse on  another spot and drag. This creates a curve. You can then right click the curve and select 'stroke path' to turn it into a line made with the same thickness of your brush.
The pen tool can also be used to easily make straight lines.

The pen tool may sound easier than making a hollow circle, but it's not. If you use it incorrectly you'll end up making loops in your curves or, if the lines are wrong in comparison to your brush, you may get an ugly line at a thin part. Making a curved point (cat's claw shape) can also be difficult to do if you don't know what you're doing (you need to tap, drag, tap in the right positions). It takes a lot of experimentation to succeed with the pen tool, even if you do know how to use it. It's not the most complicated thing in photoshop but you must make sure that you use it correctly and drag (or not drag) the mouse correctly to not make a mistake.