Fuel Flows:
Tap Settings > Aircraft Type Database > [your type] > Basic Performance.
Scroll down to the sub-section marked BASIC PERFORMANCE.
You'll find the fuel flow settings here. Make the adjustments necessary to represent the way you operate your aircraft.
When you're done, tap the back button ( < symbol, top-left of the window) two or three times, until you are prompted to save your changes. Tap Save each time you are prompted.
If the figures are greyed out, it means that there's a Detailed Performance Profile active on that aircraft. You'll need to tap Settings > Aircraft Type Database > [your type] > Detailed Performance and make the necessary adjustments to the detailed profile(s).
Fuel Reserves (Contingency and Final Fuel):
To adjust your fuel reserve settings, tap Settings > Aircraft Type Database > [your type] > [your rego]. Scroll down and look for VFR Contingency and Final Fuel and IFR Contingency and Final Fuel. Adjust the minutes or % as necessary for your flight planning needs, then tap the back button ( the "<" symbol, top-left of the window) two or three times, until you are prompted to save your changes. Tap Save.