Underglow kit: plug and play. Stick the strips to the underside of the car, run the leads to the controller box, and power the controller from the fuse box or battery (ignition or parkers position recommended). Control it with the remote or app. Grille light strips are an add on that plug into the underglow controller.
Footwell kit: powered by USB. Plug it into a USB port or a 12V USB adapter, stick the strips under the dash and seats, and control it with the app.
PRO 18in1 ambient kit: hardwired. The main controller goes behind the dash and connects to 12V. Each door has a small sub controller which you power from the window switch wiring in that door, then the LED strips plug into the controllers as labelled. The strips can be cut to length at the marked cut points. Every car is different for routing and mounting, so there is no step by step guide for a specific vehicle. If you are not comfortable with door wiring, an auto electrician or car audio installer can fit it in a couple of hours.
Use heatshrink on any join you make. Electrical tape will not last and is not covered by warranty.