Below are videos taken from YouTube that will help with your playing

First, the basics of holding your mallets the right way*, and finding the b-flat - which we will use as "do" (in the do-re-mi-fa-sol-la-ti-do scale)

* holding your mallets properly will give you the best, loudest, and clearest tone.

now; finding and playing  B-flat  ( and other notes )

NOTICE that the LOWEST B-flat does not belong to a group of three. This is only because they had to stop the keys somewhere, and they decided that low 'G' would be the lowest note. Larger xylophones and marimbas will have many more B-flats than the basic set of bells (sometimes called a marching glockenspiel, or just glockenspiel for short.

now we have a video on reading the lines and spaces of the treble clef

notice that I said 'reading lines and spaces"  NOT  "reading notes.

this is because it is the lines and spaces that are named : A,B,C,D,E,F,and G. The notes themselves are actually named only for the amount of time they are held for :
quarter note = 1 beat
half note = 2 beats
whole note = 4 beats
and so on. 
IF YOU SAW THE HEAD OF SQUIDWARD ON THE BOTTOM LINE OF THE TREBLE STAFF, YOU WOULD PLAY AN   'E'. I don't know how LONG you would hold it for, but it would be played as  'E' because ANY note symbol on the bottom line of the staff is played as   'E'

now we learn about scales;

any scale is named after the note that it starts on
it will also end on that note - for a total of 8 notes ( the starting letter name gets repeated at the end)
the closest notes on every instrument are a half step away from each other - so every note on you xylophone is a HALF step away from its nearest neighbor, up or down , so if you move 2 notes higher or lower, you have moved a WHOLE step
a MAJOR scale can be made starting on any note by following the pattern: W, W, H, W, W, W, H   (W= whole step and H= half step)

Below is the 'c' major scale

here is the  'f'  major scale

here is our b-flat major scale