To apply rules to automatically change prices go to SETTINGS->YIELD OPTIMISER and create one or more rules.
If you are using However, the yield optimiser you can set individual dates or days of the week to "manual" to does not override this price multiplier if there is a value in here already. If a value has been automatically entered by the rulesyield optimiser it will be highlighted with blue background, if it was entered here manually then there is no highlighting.