Short answer: most park benches do not come fully pre-assembled. They typically arrive in a flat or compact box with the seat slats, legs, armrests, and hardware packed separately. You will need basic tools, but nothing too heavy-duty.
In most cases, that means a wrench or socket set, a Phillips screwdriver, and sometimes an Allen key. The bolts, washers, and nuts are usually included. Plan for about 20–40 minutes of assembly, and if you can grab a second person, it makes lining up the legs much easier.
If you want a truly zero-assembly option, check for benches listed as “fully assembled.” Those often ship freight on a pallet and can cost more, but all you have to do is set it in place. For the average park bench, though, expect light DIY assembly rather than a ready-to-sit arrival.