Welcome. Those of us who use to ride with downtube shifters will tell you this - just try the STI. While it may appear more complex on the surface it really is far easier and safer. It will take you all of about 5 minutes to master.

Essentially, left is front der right is rear. Pushing in on the brake levers tightens the cable one stop (gear) at a time. The small lever releases the tension thus sending the chain the other way. This is for Shimano systems.

Brakes work the same way as always.

Go take a ride - it will be worth it.

55/Rad