We install a lot of electric under floor heating systems. It's not exactly hard but you do have to do know how to do it correctly. I'm assuming the substrate is adequate so I won't talk about that.

First you will need to have the electrics prepared correctly by a qualified electrician as it will need to satisfy building regulations, such as safe location of power and controls, and having RCD protection either at the consumer unit or locally. Your electrician will be able to advise. Next, take a multimeter and check the continuity of the mats to check for any faults before installation.

You might choose to put some insulation boards down first, especially on the ground floor; trowel out tile adhesive and put the insulation boards down, pressing out air bubbles to achieve good contact all around.

Next, (once the adhesive from the last stage is cured) starting from where the electrics are located (the tails of the last mat will connect into the controller). lay out the heating mats ensuring that you don't overlap the heated elements, and keep to around 10cm of the perimeter of the room. Do leave room for the temperature probe before you install the mats as it mustn't touch any of the heated cables. We often use loose cable rather than the mats which is a bit more flexible than mats for running around shapes in the room.

Once the heated mats and temperature probe are set-out, carry out another continuity test to check for damage and then cover them with floor-levelling compound.

After that you're good to tile.