@Shibui is right, Ginkgo trees have separate sexes. In the USA, trees brought in from Asia before WW2 were often just seedlings. In older cities like Milwaukee and Chicago (I'm mainly familiar with these 2 cities) there are a scattering of big old female Ginkgo trees. In fact, you Chicago area BNuts have a great source of Ginkgo nuts - the Frank Lloyd Wright Studio in Oak Park. Between Nov 1 and Christmas, every day a few hundred gingko nuts fall from the massive female ginkgo in the courtyard of the Frank Lloyd Wright studio. During the day the groundskeepers are meticulous about sweeping up and discarding the nuts. At night they accumulate on the ground under the tree. The courtyard is open to the street at night, just walk on in and collect nuts to your hearts desire. If you are only able to visit during the day, just ask a groundskeeper where they dispose of the nuts, I'm pretty certain if you are polite, they will show you and again you can have as many as you want. If you are in Milwaukee, there are quite a number of female ginkgo trees, in particular, along Oakland Ave, within 3 blocks of Lake Michigan. Also if you know your Milwaukee history, in 1924 the US Ambassador to Japan retired to Milwaukee, where he planted a female ginkgo in front of his huge, brick bungalow on the south side. I forget the address, but ask anyone in the Milwaukee Bonsai Society and the location of several female ginkgo trees are "common knowledge" in the group.
By the way, the use of ginkgo nuts is not just medicinal, they are EDIBLE. Delicious in fact. Preparation for planting and or for eating is the same. Collect the nuts you want to process and put them in a small bucket, cover with cold water. Important, perform all cleaning outdoors. The soft seed coat contains butyric acid and related compounds, which essentially smell like rancid butter. Not the vague smell of rancid butter that makes theater sold popcorn smell so good, but the deep, heavy pungent odor of rancid butter with "notes of vinyl" that will churn the stomachs of those with weaker constitutions. Tumble and scrub the soft pulp away. It won't all come away the first try. Change water. Allow to stand overnight in cool to cold water. Tumble and scrub the second day, discard water, replace with cold water. Third day tumble and scrub - if most of the odor is gone, they are clean enough. If odor is objectionable, repeat the process until odor of drained nuts is mild enough to not offend the nose. Seed are now ready to stratify or to cook.
I stratify seed in plastic bags with damp sphagnum, placed in the refrigerator over winter. Plant them out in spring the same time one would plant out acorns for oaks or other hardy tree seeds. I place pots in a wire cage to keep squirrels from absconding with the nuts. Squirrels and other critters love eating ginkgo whether stratified outdoors in autumn or in spring. Leaving the stinky seed coat on and just planting out in autumn works well too, but squirrels with eat them even with the stinky seed coat, so wire cages are mandatory.
If you want to use ginkgo nuts for a delicious treat, you can crack the cleaned nuts like hazel nuts with a nut cracker. The meat is a single kernel, and it is pretty easy to extract. I actually usually boil the whole nuts in water for about 20 minutes. Drain and allow to cool. They crack more easily after boiling. I then store the cooked kernels in the refrigerator. I sliver them and put them in soups, stir fry, stews and anywhere you want to add a little different texture. Flavor is mild. I use them much like one would use chestnuts.
Ginkgo trees do not begin producing nuts until about 30 years of age. The first "common" use of them as landscape and street trees did not happen until about the 1910 to 1930's. So by about 1950 most nurseries suddenly realized that planting seed to obtain ginkgo was a bad idea. That's when they began propagating ginkgo by grafting or rooting cuttings. When looking for female ginkgo trees, don't bother looking at trees planted after about 1960, as these will almost always be male trees. Find the older ginkgo trees, that is where the female trees will be.
So go nuts, collect ginkgo nuts.