To add new text field, please enter field name, select Type: text, select page section from a drop-down list:
Then choose is this field is mandatory to fulfill or not mandatory and set to Yes the field Search support if you want to be searchable and visible by Estatik Search Widget.
If you did everything correctly you will see your new field in the right column in the Basic section:
and in Add new property:
In frontend it will be look like any other text field: