Since sitefinity had an Fluent API for different module.
But if i create a new custom module from sitefinity, did that module also has API?
Yes, each module created through the Module Builder has an API too. The documentation for that API will automatically be created. Click the Code Reference link in the module to see it.
Working with something like FileHelpers will make it easier to read and loop through the csv, xsl files. Download here
After set up the FileHelpers will have a Class with properties for each column you can then loop through the rows and access the columns data adding it to sitefinity with the API that Arno pointed out.