usually the data format just contains all values blank seperated, one example per line.
But since RapidMiner uses regular expressions to split the values, we could use the regular expression "\s+[0-9]*:" to use the blank, feature names and the : as seperator.
This is only possible, if your formate is not sparse, does not leave out some features or rearrangs in different lines them!
Use this as regular expression in the ExampleSource ConfigurationWizard.
For the rest of the processes, take a look on the samples shipped with rapidMiner.