The Convert Tab dialog is split in half with the Input settings on the left side and the Output settings on the right side.
The drop down menus will contain the names of the columns in the table. Using the drop down menus, select the column name that relates to the appropriate data type. If the table was loaded with no column names, default names will be used (C1, C2, etc) in the menus. The Calculator will label the drop down menus according to the coordinate systems that have been set in the Point Database Conversion Job. For example, if you are converting geodetic points (Lat/Long), the text boxes will indicate "Geodetic Latitude" and "Geodetic Longitude". For grid (UTM, State Plane, etc) the labels will indicate "Northing" and "Easting" where appropriate. This is true for both the Input and Output sides of the dialog.
On the Output side of the dialog, you can either select existing columns in the table to overwrite, or use the Add buttons to create and name new columns. Scale Factor and Convergence are optional output fields that only apply to projected coordinate systems.