Okay, so if the diagram had O’s across the whole thing, then you wouldn’t even have to touch the fretboard at all, you would just strum it. However, this diagram has a couple of other marks on it, and those indicate where we need to place our fingers. In this case, they are on the 2nd fret of the 4th and 5th strings. The frets are the metal parts running perpendicular to your fretboard; they are what the string makes contact with when you press your fingers down. On the diagram, the frets are the horizontal lines. So count up to the second fret, and put your fingers down just behind the fret, like in the diagram.
The simplest answer and the one that no student that ever wants to hear is practice. Changing chords is the process where many beginners fail, and quit. But after that, the rewards will be simply impressive. There are a few tricks to get a chord transition to happen faster. Use a metronome: Set it on four beats and set it as fast or as slow as you want. Then get a chord in your mind, say D. When the metronome reaches its last beat, press down the strings. When it happens again, strum it and let it free. Then again. Do this 10 to 20 minutes a day and in less than a week, the chord progression will begin to sound much better.
Use tabs instead of sheet music. If you don't already know how to read music, it can take a lot of time to memorize and proficiently read sheet music. Tabs are an easier and more intuitive way to write music for beginners that doesn't require any formal education. Tabs will simply tell you where to put your fingers on a fret board and how to generally play a song.
Practice playing individual notes. Holding down a string and producing a decent sound can sometimes be more challenging than it looks. If you don't hold down a string hard enough, you'll get a muted note and if you hold down the string too close to the fret your guitar will buzz. Practice picking in an up and down motion on your string with the other hand. Continue doing this until you feel comfortable moving up or down the neck to a different note. Practice playing the notes back and forth until you become comfortable strumming.
These beginner guitar lessons cover everything you need to know in order to get started playing the guitar. You'll learn the basics like how to hold the guitar, how to tune a guitar, and what all the parts of the guitar are called. Then you'll move on to learning essential guitar chords, strumming techniques, and how to put everything together to play your first song. These beginner guitar lessons are essential for anyone that has always wanted to play the guitar, but never knew where to start.