STEP 3
Now create a new layer by pressing Ctrl+Shift+N/Cmd+Shift+N. Press D to make your black as your foreground color and white as your background color. Now press Ctrl+Backspace/Cmd+Delete to fill the new layer with white color. Press Ctrl+D/Cmd+D to deselect the selection.
Rename “layer 1” to “stroke”.
You may now turn off Grids.