What CT says, but if you haven't got a spanner to hand it's still easy without.
Remove box
Put Shifter in gear 1
Replace box
Turn as far towards 14 as it will go
Remove box
Put shifter in gear 14
Hopefully both hub and shifter are now in the same gear
It's worth getting the hang of this as it's easily moved when fixing a puncture and you might not always have a spanner with you!
If it was all working before, it should all be working now, you shouldn't need to make any adjustments. If it isn't working, something has changed, it's possible an inner cable isn't seated properly in the outer, or in the shifter. I wouldn't start adjusting cable tension till you've eliminated all other possibilities, though it's not impossible it was working fine when something was out of place and the problem now is you've unwittingly fixed it!