#491 in Stitch World - If you need to program this stitch pattern into your machine, check your manual under "How to Program" for your machine.

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Negative Key  Check your instruction manual under "Variation Keys" for the location of the Negative Key on your particular machine.   When you push it, it will keep the needle that will be tucking in B position, and the other needles will be in D position.

Ribber set on H/5 - If you look at the bottom left side of your ribber bed, you will find a button that slides back and forth between P and H.  In order to knit with 72 needles on both beds, the needles on the ribber bed must slide in between the ones on the main bed.  When they are in P position, they bump into each other.  When they are in H position, they slide in between.  Set the button to "H" for knitting the scarf. 
     If you look to the left of the needles on the ribber bed, you will find little indicator numbered 0-10.  The red indicator needs to be set on 5 for most of your knitting projects.  Below the ribber you find a handle.   If you turn it back and forth, you will notice that it moves the red indicator line.  Be sure it is set on "5" for this project.

Zig Zag Row - After you have done all steps above, knit one row from right to left.  This is your "zig zag" row.

Circular Rows - This means that you are knitting on one bed only for three rows.  Push in LEFT Part Button on main carriage.  Push up RIGHT Part Button on ribber carriage (the one on the right side that says N on the bottom and P-R on the top).  Knit to the right.  You see that it knit only on the main bed.  Now knit to the left, and it knits only on the ribber.  Knit one more row, and it knits only on the main bed.  This completes your 3 circular rows.  Carriage is on the right.  Release Left Part Button (using "Plain" button on main carriage), and push P-R back to N position on ribber carriage.

Setting your tuck pattern - Enter the pattern number you will be using (Check under "Pattern Program Procedure when using Selector I) in your manual).   With the carriage on the left side, turn the Change Knob (the round white knob on the right side of the main carriage) from N (used for stocking stitch, lace and intarsia) to KC (used for fairisle, tuck, tuck, skip, weaving, thread lace, etc.)   Select the Negative Key (see above).  As you knit to the right, the needles will be selected in the pattern.  When you are back on the right side, push in both Tuck Buttons.  Now you are ready to knit your 420 rows.