HTML Conversion takes just three steps: Files Selection, Confirmation and Process Completion.
Conversion from Natural files is not available yet.
This is the first step. Just select the files you want to convert on the left panel, click the Add button and, finally if everything is right, click Continue.
You can select up to 1000 files to be converted at the same time.
This step is intentional, and it is designed to make sure that the files selection is correct. You do not want to waste valuable time waiting for unnecessary files to be converted to HTML.
This is the final step. And usually takes few seconds unless you select several files to be converted. It generates a ZIP files with all your final HTML files and extra basic CSS and JS files in order to make the final result more versatile.
If a BMS file cannot be converted, its HTML version will be created with an error message, and an extra file named issues.txt will include all conversion errors or warnings that were detected. So make sure you open that file before going further in your development.