I just got a new guitar from eBay, it is a classical acoustic guitar. I am trying to tune it, but strings are going out every time I tune them. I could not even play it yet, because every time I strum, strings go out and they do not sound like they should. I am a beginner and I do not know what is the reason. Should I be angry and return the guitar, or does it need time to get "fixed"? Thank you.
They could be slipping at either end. Give them a firm pull - not a yank - and keep re-tuning. Then repeat. It's normal for new strings to do this, which is why we tend not to change strings a day or two before an important gig!
They need to be wrapped around the tuning peg properly to avoid slipping. Also, does your classical have machine tuning pegs with metal gears or wood pegs like an old violin? Some classical guitars have wood pegs and friction between the peg and the head is the only thing keeping it from slipping. These are hard to keep in tune.
Aside from wrapping the string properly we sometime intentionally force the string to wind over the loose end in the tuning peg to hold things in place. You might want to look up a Youtube video on correctly stringing a classical. If it came with strings on that doesn't mean they were put on correctly.