If you are using Sawtooth Software's hosting service then you shouldn't need to specify the database username. You should be able to upload your survey just by using the first tab named "Sawtooth Software Hosting" on the "Hosting Management" dialog.
If you are hosting on your own server, then you will need to have a database user that Lighthouse Studio can use to store the respondent data. You will need to specify the username and password for this database user on the "Self Hosting" tab of the "Hosting Management" dialog.
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