If you mean trying to write into the csv file, we used a StringBuilder to build a string that contained all of the information that we needed to put into the csv. Then we used s.append(",") to change the columns. (where s is the StringBuilder)
As a whole, we had a FileWriter to which we appended the StringBuilder.
If you just mean to go across the columns, then add a comma to whatever you are using to write the csv file. (CSV stands for comma separated values, so you need a comma to separate the values).