MARIN FAIRFAX SC 2 NEXUS INTER 8 HUB

[colinbow]

Hi I have just bought above and want to adjjust gears Youtube vids say put in 4thgear and this should line up 2 yellow markers Seemed straight foreward but my bike has no yellow markers at all There is a plastic window where one should be but no yellow line Any ideas? I am a 70 year old with no camera facilities so cannot send pics Colin