Tools and Common Workflow

Kicad includes other two important tools:
"cvpcb" is used to associate footprints to components
This is a boring but necessary step in the design workflow
A well-written component already lists the few possible footprints
"gerbview" (or "gerbv", from the geda suite) can be used to verify your output
Never ship a gerber without looking carefully at it

So the standard workflow looks like this:
eeschema: make the schematic diagram and save the netlist
cvpcb: read netlist, associate footprints to components
pcbnew: read netlist and footprints, make the PCB and plot gerber files
gerbv[iew]: check the output
email/web: ship the files and wait for the PCB to reach you

Finally, mounting
Either you buy components, and solder yourself
Or, at extra cost, you buy components, pack them again and ship for mounting
For this you need the BOM an position files, saved by pcbnew
Or, at extra cost, your manufacturer does everything for you
You must be most precise with your BOM file