In katalon studio, you have inbuild method to read data from excel file as well, you can point an excel file with test data and your in test data tab, you can create a new variable.
Say username and password,
You can call above variable in the script as,
{
"username":username,
"password":password
}
make sure that your header, i.e. the first row in the excel file and the variables you are creating are the same.
You can go through this video to get a visual,
https://www.youtube.com/watch?v=XoCzZRdEKqM