Each .VWR file has its own language. Each Aligner file (.ALI) has one language for each of the component sections. (They could all be the same, if for example you were analysing various different editions of a Shakespeare play they'd all be English.) The set of languages available is that defined using the Languages Chooser.
You can change the language to one of your previously defined languages using the drop-down list. Here is an example where a Portuguese language plain TXT text file was opened and the default language was English.
When Portuguese was chosen in the drop-down list, and
agreed to, it was possible to save the result (as a .VWR file) so that henceforth it would know which language to use.