Creating own elements

I need to create own element and put it in the specification.  A similar form is present in the specification, but I need to modify it

1. Where should I draw it ? In which format?

2. In which directory should I put this image?

3. I noticed that the symbol images are stored in the directory c:\Program Files (x86)\Bentley\Plant V8i\Modules\Base\pictures\ following are the form

I also need to create these symbols?

Thanks