Here is the main guitar part for this famous song. It is played with a style of fingerpicking called Travis Picking (after Merle Travis). This is a great technique, and worth learning as it helps you rhythmically diversify from standard pattern picking.
Essentially the Travis picking pattern involves playing an alternating bassline with your thumb, whilst using your 1st and 2nd fingers to play the melody line. Pay attention to the ActionTab, and use the Tablature view to get it down quicker.
Familiarity with the song will help you get a feel for the Travis style. It is important to have the pace / feel the music in your mind whilst practicing because it is more rhythmically complex than standard T123 based patterns such as House of the Rising Sun or Stairway to Heaven etc. It will take work to crack it. But once you have the hang of it, the rest will flow much easier.
Work at fingerpicking though the first chords over and over until you get the Travis picking going well before moving further into the song. Practice between here (C major) and here (the end of the C maj7 chord). Repeat until you can get a decent fingerpicking speed up (notice you'll need to remove your 1st finger on the fretboard to change between the C major chord and the C maj7 chord halfway through). Don't forget to use the Tablature view to see the structure of the fingerstyle better.
Once you have this first bar down, you'll find the rest of the song will be easier to do. The same fingerpicking pattern applies throughout the entire song. The rest is just cycling through a fairly simple chord progression (here's the start of the song):
C - C maj7 - C add9 - C
A sus2 - A sus4 - Am - A sus2
Although the picking is fast (check out the normal speed audio to get the full pace), you are really just fretting one main chord type (e.g. C major is the first chord type) and then fingerpicking through various alterations of this basic chord type. i.e. adding or removing fingers on the top strings to move between C - C maj7 - add9 etc. So stay in the C shape position for the first few bars and add / remove fingers on the B string.
The same thing applies to the next main chord type (A minor based). Just hold the basic A shape on the fretboard, and add or remove fingers along the B string whilst keeping that Travis picking tight!
Once you can do the start / intro, you'll find the rest of the song straightforward for the most part, but still challenging to practice. Some of the chord changes will take work to get smooth! If you are a new beginner you should work through the Core Skills section on fingerpicking (at least) before attempting it. It's a very good song for helping you develop technique and consistency, but only when you are ready for it.
A quick word of warning about the outro....notice that the top E string is fingerpicked regularly using your 3rd finger. Here we change the Travis picking style to switch between Thumb, 2nd and 3rd fingers instead of Thumb, 1st and 2nd fingers. Although you can keep using that, we recommend you use the fingers shown here.