To configure a new-added or existed element you should use Properties/events pane.
Select an element in the Components tree and its available properties/events will be presented in the Properties/events pane. Once visible in the Properties/events pane, these values can be edited.
You can select a property by clicking on the property title or value. When a property is selected, an editor is displayed instead of the value and the value can be changed. In most property editors Enter should be used to apply the value, and Esc to return to the previous value.
Form configuration is given individual consideration. The reason - its own inner designer for adding and configuring form controls (the common technique of configuring can be applied as well. Inner designer is just an alternative way). For details see chapter 'Form designer'.
For information of accessible properties/events, please refer to the related component documentation.