I prefer the term time-restricted eating. Intermittent fasting could relate to a number of approaches, of which time-restricted eating is a subset. Any time someone uses the term intermittent fasting, they need to follow up with a paragraph explaining their selected usage of the term.
The easiest way to start with TRE is to hold off any meals after 6 p.m.
That includes avoiding alcohol or anything that would produce caloric intake (sweetened tea, for instance).
That does not include items with zero or negligible caloric value – water, plain tea, plain coffee
Once you find yourself comfortable with the 6 p.m. cut-off (takes about a week), move it up by an hour to 5 p.m. Then up by another hour. My current hard cut-off is 2 p.m., but I frequently end up eating a big lunch noon’ish and finishing up way before 1 p.m.
Once the forks (spoons, knives, chopsticks) are down for the day, track your fasting period. I use Zero, but any time tracker or Google Sheet would work. The fast starts when the last morsel of food is consumed and stops when first calories start hitting your stomach (that buttered coffee in the morning, or, if you choose your coffee black, a meal afterwards).
A documentary The Science of Fasting is included with Amazon Prime Video. There are some extreme experiences there, spanning multiple weeks of water-only fasts. Don’t try this at home without some medical supervision, but it’s worth watching nevertheless just for the science aspect of it.