Unable to select a tabular dataset

Good morning. It is my first time using Galaxy/hutlab. I have uploaded a text tab-delimited file and it apears in my history. I am trying to use it to perform the first step of LEfSe (A. Format data for LEfSe) but i am not able to select any file as the drop-down menu does not work and doest not appear when I click on the first option. I can not select either which rows have to be used as class or subject (I am not able to select anything in the items on the red circles). Should I do anything else before this step appart from uploading my text tab-delimited file?

Thanks.

You need to change the datatype of your txt file. You can do that by clicking on the pencil icon of the file. After that a new window will appear, on top of that window you will find some tabs, choose the datatype tab.