Practice at least 20 minutes 6 days a week. Consistent practice will allow you to improve your guitar playing skills over a short period. Taking long breaks and not staying dedicated will wear away your muscle memory and delay the development of your skills. Instead, dedicate 20 minutes to an hour of practice throughout most of the week. During practice, you can either run different drills or you can try covering a song.
Your success on guitar, or anything in life, is directly related to the effort you give. Is it true that some people are more gifted than others when it comes to music? Of course, but don’t go around thinking you can't learn guitar because you weren’t born with the right musical aptitude. That's nonsense. Some people may be more gifted, and you can't control that. What you can do is control how hard you work, and promise yourself that nobody will ever outwork you.
Position your fingers on the neck. The dots on the chords represent where you should hold down your fingers on the neck. For instance, an A major is played by holding down the string on the second fret on the 2nd, 3rd, and 4th string. An E minor is played by holding down the second fret on the 5th and 4th string. Hold the strings down until they are pressed against the neck of your guitar.
There are hundreds of free guitar lessons here and it's taken a lot of work over nearly 15 years for me to create it all. It's important to me to help everyone that wants to learn to play the guitar, not just those with money for tuition, so I run it on an "honour system" and I rely on the honesty of users like your good self to make a donation if they can afford to.
As a beginner, it is best to avoid making a pawn shop, flea market, or yard sale purchase unless you are shopping with somebody who has experience in purchasing a guitar. Having never purchased a guitar, you may not know what to look for in terms of damage or guitar quality. With that being said, a local music retail shop is your best bet. You may also shop online with a reputable company, although be sure to review the business’ return policy.