I cannot find a barrel adjuster on my bike I tried to adjust the cable tension but there it litterally no way to adjust it on the front derailleur on a 22.5" GMC Denali 700cc Men's Bike

Generic photo from walmart.com
You might not have one. Check near the place where the cable exists the front shifter or on the cable, but on a BSO like this, you most likely don't have one. 

Your options are to install an (inline) barrel adjuster or just do the adjustments without the barrel adjuster (which just allows for fine tuning, really -- you can do all the adjustments without it, but they will be finickier).