Modern electronic bidets are easy to install because they tap in to the existing cold water valve which refills your toilet's water tank. Moreover, you don't need a separate drainage system since the bidet's water just falls into the toilet bowl.  

There are three main components to electronic Toilet installation - (1) taking some measurements of your existing toilet to ensure proper fit prior to ordering, (2) mounting the bidet onto your toilet and (3) connecting your bidet to the existing cold water supply.
The first and most important measurement is the measurement in the back, where the rear of the bidet will sit. You'll notice two caps behind your existing seat and beneath these caps are bolts which secure the toilet seat to the toilet. Measure the clearance from your water tank to the center of these caps. Most bidets require at least 1.5 inches of clearance from the front of the water tank to the center of these caps.