Got my 1st new bike delivered. Got it all assembled but having trouble adjusting the front deraileur on my 21 speed.

The front chainwheel has three chainrings. I can manage to get the bike to shift from the smallest ring to the middle, but not all the way to the largest. Or I can get it to be on the largest, but cant get it to shift down to the smaller two rings....I can set it either one way or the other but I cant seem to get it so the derailer can move the gap required to move the chain to any/all three rings....

When I have it set so it can shift from the smallest to the middle ring, it seems the deraileur has reached it's furthest most outer limit - When I set it so it can reach the largest ring, when I go to shift to the other rings the cable loosens but nothing happens......

Tried all sorts of combiantions of the H and L screws.......just could not get it.

The front shifter is a Revo Friction Shifter if that makes any difference. The Deraileur is Shimanno.

Also.....NEWBIE rider here........and taking to a bike shop is not an option at the moment......

Going to read thru directions again, watch some you tube videos, and try again tmro with fresh eyes and attitude......but any tips appreciated.

I must be doing something wrong