To modify your pie's target values go to the 'Holdings' screen and tap on the 'Edit Pie' button:
You will enter the 'Edit Pie' mode and you'll be able to use the sliders to adjust the target values of your pie. The sum of all targets must meet a total of 100%.
When you are ready, tap the 'Save' button.
Updating the target values will not trigger the buying or selling of any investments. If you want to enforce the new allocation, you will need to rebalance your pie.
The new fund contributions will be distributed according to the new target values.