The trailhead sign had a QR code taped over what used to be a phone number, presumably updated after the visitor center moved somewhere, though I never did find out where.
Your first day
Pick a flat, well-marked loop or out-and-back trail under three kilometres in total, and check it on a map app beforehand. Wear shoes with real tread, not flat-soled sneakers, and socks that aren't cotton, and bring water, a charged phone and a small roll of blister tape. Check the weather and sunset time, and tell someone where you're going and when you'll be back. Walk the whole thing without rushing, paying attention to how your feet feel the entire way.
Most people ignore a hot spot on their foot because it doesn't hurt yet. Don't. That faint rubbing feeling, left alone for even another kilometre, becomes a blister that ruins the rest of the walk and sometimes the next few days too. Stop and tape it at the first sign.
The thing most people miss
My first real problem on the trail was gear rather than fitness: the wrong socks caused more trouble on that first short trail than the distance itself ever did. I'd borrowed those particular socks from a friend who was moving across the country that month and had a drawer of extras to give away, nothing to do with hiking at all.
After that I started paying more attention to socks and shoe fit than to how far or steep a trail looked on the map, since that's what actually determined whether a hike felt good or miserable by the end.
What not to buy
Don't buy trekking poles or a fancy pack before real tread. Shoes without grip are the actual first mistake most beginners make, and no amount of gear further down the list fixes shoes that were wrong from the start.
By the third trail, I finished a hike almost half again as long as my first one and checked afterward to find zero hot spots, where that first short walk had given me two, this time in a pair of socks I'd actually bought for the purpose. Elevation gain, trails measured by climb instead of just distance, changes the effort completely, and it's the next thing worth paying attention to.