yes. Insert beat button (bottom of web editor) will move everything along. Do this a few times obviously. You can insert a barline either left or right of any space you are in with the blue cursor with the Add button.
Also you can use the Copy and Paste buttons for your intro, if the chord sequence already exists. Paste insert can be used on beat 1 of measure 1 for instance, where it will copy your selection and simultaneously move the existing measures along.

Also from your device when playing back, you can long press from any measure to start playing from there (meaning it could be the last 8 bars from the end) which might be useful as an intro.