A couiple of questions first.
Was the pedal spongy before you changed the pads?
If no, then the problem isn't in bleeding.
If yes, then you need to bleed the brakes.
Did you machine the discs before fitting the new pads.
If no, then there is your problem, get the discs machined to remove any ridge and bumps as the new pads are flat and your old disc would have valleys and ridges.
If yes, then go back to bleeding.
To bleed get a one man bleeding kit from your local parts shop.
The bleed nipple is at the rear and top of your caliper.
Place car, front or rear or both on stands.
Firstly using the correct size "Ring" spanner (not an open end spanner) crack the seal on the nipple, it may be quite hard to undo.
Once cracked loose, retighten lightly.
Now attach bleeding hose to nipple with your ring spanner still on the nipple.
With hose and spanner in place undo nipple and leave open.
Next make sure Master cylinder is up to full mark, if not top up with fresh brake fluid.
This is how I do it by myself.
I place my left hand on the brake pedal while I look under the car in the direction of the wheel being bled and pump the pedal until i se no air bubbles flowing in the stream of fluid then stop pumping and go around and tighten the nipple closed.
Now test the pedal with your foot, does it feel better.
Repeat for each wheel, starting with wheel to be bled closest to the master cylinder.
Thats how I do it and have never had a problem.
Just fitted and bled HSV/AP racing barkes to my Senator this way.
SW