Brake problem i just change the rear brake calipers in a jaguar x-type 2002 and the brake pedal goes all the way to the bottom floor what seems to be the problem?

Hi this is air in the system if you pump them do they go hard as normal? what you will need to do is , starting from the furthest caliper away from the fluid bottle you have to bleed the air out, you can buy bleeding systems for a few bucks/pounds but you can also do it yourself, to do this, find a length of small bore clear hose/pipe, locate the bleed nipple on the caliper, find a wrench/spanner that will fit the bleed nipple, put that on first, then get your pipe/hose, and slide that over the end of the bleed nipple ( make sure the pipe/hose is a nice tight fit ) locate a small clear glass jar partly fill it with brake fluid, put the hose/pipe into the jar so the fluid covers the end ( we don't want air to go up the pipe/hose ) then get a friend to pump hard on the brake pedal till it goes hard, and when it does tell them to keep their foot hard on the pedal , you then undo the bleed nipple ( you should get some fluid come out fast) when the pedal reaches the floor ( this happens immediately if you have opened the nipple far enough, then when it has hit the floor do the bleed nipple up again before they raise the pedal keep doing this till you see no bubbles coming through the hose/pipe, repeat the operation on the next furthest away, and so on till all the air has been removed from the system, be sure to check the fluid in the reservoir regularly as this will cause air to get back into the system again if it runs to low....hope this has helped and good luck, please vote thanks