If for a particular month the Tax deducted is zero and you want to file the TDS return (24Q) then you will have to update the Nil Challan. This is a challan with zero amount.
Steps to be followed -
1. Click on the "Update Nil Challan" button as shown below
2. Fill up the details including the Certificate you have got from TRACES
3. Till you have not used this Nil Challan in a 24Q you can edit or delete the record
For details on how to generate 24 Q - refer article.