Adjusting bike gears can seem daunting at first, but with a little patience and attention to detail, it's a task that can be easily accomplished. Here are some general steps to adjust bike gears:

1. Shift to the smallest chainring on the front and the largest cog on the rear derailleur.
2. Use the barrel adjuster on the rear derailleur to adjust the cable tension. Turn the barrel adjuster clockwise to increase tension and counter-clockwise to decrease tension. The goal is to achieve smooth shifting.
3. If the chain is not shifting up to the larger cogs on the rear derailleur, adjust the high limit screw on the derailleur. The screw is typically labeled "H" on the derailleur. Turn the screw clockwise to move the derailleur towards the wheel and counter-clockwise to move it away from the wheel.
4. If the chain is not shifting down to the smaller cogs on the rear derailleur, adjust the low limit screw on the derailleur. The screw is typically labeled "L" on the derailleur. Turn the screw clockwise to move the derailleur away from the wheel and counter-clockwise to move it towards the wheel.
5. Once the high and low limit screws are set, fine-tune the shifting using the barrel adjuster. Shift through all the gears and make small adjustments to the barrel adjuster as needed until the shifting is smooth.
6. If the shifting is still not smooth, check the alignment of the derailleur hanger. A bent hanger can cause shifting issues.

It's important to note that these are general steps and the specific process may vary depending on the type of bike and the components used. If you're not comfortable with adjusting your bike's gears, it's always a good idea to take it to a professional bike mechanic.