A few questions about installing engineered hardwood
The installation instructions for that product which are provided on Home Depot's web site indicate that this floor is intended for either floating or glue-down installation.
As such, no nails or staples are appropriate or necessary.
The instructions also specify a 1/2" expansion gap.

The fact that you're asking about taped underlayment strongly implies that you're not intending to glue it down - so (unless you're planning to go against the manufacturer's recommended installation instructions and nail it anyway) you should be doing a floating installation over the underlayment.  

Some underlayment has pre-glued strips along one edge which you use to stick the pieces together, but obviously this doesn't always cover every join, so you'll probably need at least a little tape to finish off.
You should be able to buy this tape along with the underlayment.