Yosemite, an Unesco World Heritage listed National Park, is located in the Nevada mountains of north-eastern California. Covering 1,200 square miles and with almost 4 million visitors every year, Yosemite is a majestic place with many outdoor activities and some good hostels.
There are some airports close to Yosemite (Fresno, Merced and Modesto City airports are the closest ones), but no actual airport in the National Park itself. There are train and bus services connecting to Yosemite. You can also drive there yourself, if you have a rental or your own car at your disposal. There are four points of entry to the National Park, but be sure to fuel up before entering, since there aren't many gas stations around and the ones that do exist, sell their gas for a hefty price. The hostels around Yosemite are located in some cases a ways from the park, so a car is a good idea.
Yosemite is home to Yosemite Village, which is the place to start your excursions (if you're into hiking, which is by far the biggest pastime of people traveling to Yosemite). You should check at your hostel or at the information center before taking to the trails, the rangers are a great source of information and they also have the most recent things to know (if some of the trails are closed or if there are weather advisories, etc.).
After choosing your activities and where you want to go in the park, you can park your car (if you have one) and take the free shuttle bus to your destination. The transportation system inside the park works really well and it's highly recommended to make use of it, because some parts of the park are not allowed for personal vehicles. The shuttles run until late, but be sure to check the schedule so you won't be left behind.