There are a few ways to accomplish an import into a table.
The first one is only available on design sites. I have a included a screen shot that shows how to right click the table (when you are not entered into the table) and select the import button. this will open up a window where you can import a file.
The other way is to add an import button onto the table through the properties. On the display tab, check the import selection on the button category. I have also supplied a screen shot as this as well.
The file that you chose to upload will most likely be an excel file. Please make sure that it contains all of the columns that the table you are importing into contains. They do not have to be in the same order, but the labels of the columns do need to match.