The installation on the 3 Series Coupe is not easy if you have large hands as there is minimal space to work in, but the Hellst XRT's have vertical indentations in them which allows for a screwdriver to help you turn them into position.
The easiest way to make sure that they are lined up is to first remove the halogen bulb, then attach the new Hellst XRT H8 bulb and rest it into the opening where the halogen bulb came out. Turn on your daytime running lights so that the Hellst XRT lights up and then look through the front of the headlight to align the bulb into the three slots. Once it is aligned, turn the bulb so that it fits snuggly into the opening. If it isn't correctly aligned, the outer ring won't get the full brightness so you will know that the bulb needs to be adjusted. For the other BMW models like the X5 and X6 there is much more room thus making it a much easier install. Once they are in they are well worth the bit of time required to install them! It is definitely a DIY project.