Tap and hold (long press) the address field while it's unfocused.
Or focus the address field first (tap once), then tap and hold.
Please tell us in which of the menus you find the copy function for future reference?
And if you can't find "Copy" in the menus that open, look for a "edit" or "insert symbol" function, I remember some options like that used to bring the stock text field edit of the phone where you can access the native copy/paste/etc. There used to be an advanced option to enable/disable the Opera keyboard, disabling it (if it still exists in Mini for Java) should also bring the native text edit field where you can find all these options if your phone provides them.