Mention an evening routine and people picture a long list right away, skincare, reading, meditation, all at once. Starting with that much usually gets abandoned within a few days.
In reality, one fixed step is enough. Something as simple as dimming the lights at the same time every night with the same sound starts sending your mind the signal that the day is closing.
Once that one step settles in over a few weeks, adding others becomes much easier, because now there's a steady foundation to build on.