The simplest start for me was walking. Find somewhere appealing like a park/trail and do what you can at first. I found mornings the least likely to be interrupted by other life events.

Once you feel like the time it takes is more of a limit than the energy, find something that's more energy demanding.

For me that was cycling.

As everyone says, consistency is one of the key things to keeping the habit. I made it a M-F thing, with weekend rest days.

The other aspect is obviously diet but that is harder to suggest without knowing more about you/your lifestyle/etc.

I do think food is an easier one habit wise: if you treat yourself (or slip, however you see it) one day, I think it's easier to get back into healthier foods the following day (unless you buy everything the day you eat it?)

Anyway good luck, it's definitely worth the work.