Shift gears to the outermost rear cog and front chain ring. The chain should now be furthest from the inside of the bike.
Use a 5mm Allen wrench and loosen the cable anchor bolt on the rear Sora derailleur. The anchor bolt can be found by following the rear shifter cable to its terminus at the back of the bike.
Turn the barrel adjuster all the way into the body of the derailleur. Then give it two turns in the opposite direction. The barrel adjuster resembles a small "barrel" and is located where the shift cable enters the body of the derailleur.
Pull the end of the cable taught with a pair of needlenose pliers, and re-tighten the anchor bolt over the cable.
Shift the rear gear to the next cog over. If the chain does not shift, turn the barrel adjust counterclockwise until the shift is completed.
Shift the rear gear so that the chain is in the center rear cog. In this position, the upper derailleur pulley should be centered directly beneath the chain. To adjust, turn the barrel adjuster counterclockwise in the direction the pulley needs to move.
Shift the chain to the innermost rear cog and front chain ring. This will place the chain closest to the inside of the bike.
Use your 5mm Allen wrench to loosen the cable anchor bolt above the front derailleur. Again, if you're unsure where to find this bolt, follow the front shifter cable from the shifter to the front derailleur.
Turn the barrel adjuster all the way in to the frame of the bike. The barrel adjuster will be located midway along the shifter cable, attached to the bike frame. Once the barrel adjuster is all the way in, back it out two turns.
Pull the end of the shifter cable taught with your needlenose pliers, and re-tighten the anchor bolt over the cable.
Shift to the largest front chain ring. If the chain does not shift, turn the barrel counterclockwise until the shift is complete.