Setting Fields Using Rules
The action you are looking for is "set a data value". You will find that some values are easy to set with this and some are not. Install devel (if you havent already) and use the page array functionality to get the exact details about fields you want to fill in. Also make sure to have tokens/entity tokens available as that will make your life a lot easier for setting values in rules. If the field is multi value then you will need to start using variables, lists and loops to fill the field with data.