The table dialog box has a selector that allows you to make a nature node deterministic or probabilistic (i.e. a chance node). If you use this selector before you have entered anything into the table, it will just modify the dialog box to be suitable for entering deterministic or probabilistic information. If you have already entered a relation, that table will be converted.
Converting a deterministic table to a probabilistic representation is simple: each row of the result will consist of all zeroes, except a single 100% entry at the state the original deterministic function mapped to.
Converting a probabilistic relationship to a deterministic
one generally loses some information. For each parent configuration
the deterministic value will be the state that was most likely in the
probabilistic table (i.e. had the highest conditional
probability).