As a beginner, it's good to get into the habit of tuning your guitar by ear rather than with an electronic tuner. This helps develop your musical hearing as well as not leaving you in a fix when you're in a situation where no one brought a pocket tuner and you need to get your guitar in tune quickly. There are multiple methods for putting your guitar in standard tuning, yet the popular "fifth fret method" and harmonic variations are the most useful and simplest.
In order to use the fifth fret method properly, one places one finger on the "E" string (the lowest) on the fifth fret and plucks it first while quickly plucking the next string up (the next-highest string, or "A" string). This second string should be plucked open (not being touched anywhere on the fingerboard). Adjust the tuner for the open string until both strings emit the same pitch when plucked together. Continue doing this for each string moving up the fifth fret. For example, place one finger on the fifth fret, "A" string and pluck that one while also plucking the open "D" string and adjusting the tuner for the "D" string until it and the "A" string also have the same pitch when plucked in tandem.
Tuning this way becomes a little complicated when you make your way up to the "G" and "B" strings. When tuning the "B" string, place your finger on the fourth fret of the "G" stringnot the fifth fretbefore tuning the open "B" appropriately. This is due to a phenomenon known as the "B-string barrier," but what's important is that you become accustomed to tuning the "B" string in this fashion. When tuning the high "E" string at the top, the "B" string is first plucked on the fifth fret before the open "E" as per usual.
Another method used to get your guitar in tune without an electronic tuner is to use harmonics on the twelfth fret while plucking individual notes on the seventh fret and adjusting your tuners as needed. For example, if you pluck a harmonic over the twelfth fret on your low "E" stringachieved by just touching the string over the twelfth fret, but not pressing down on itand quickly pluck a note on your "A" string on the seventh fret so that each notethe harmonic and the actual noteare heard simultaneously, you will know whether each string is in tune by whether the pitches match. Adjust the strings accordingly before moving up the twelfth fret for each string. When you get to the "G" and "B" strings, you must again consider the B-sting barrier and pluck the "B" string on the eighth fret rather than the seventh to be sure it is in tune. Whichever method you usethe fifth fret method or harmonicsyou will assist your ear in recognizing different pitches and the soundsof different notes. This is a skill that will become indispensable as you begin emulating the styles of others and, subsequently, creating your own compositions.