An air carrier flight crew reported failing to call ramp because of difficulty using the electronic flight bag while taxiing to the gate in DEN.

Narrative

We were on our first flight of the day to DEN. Neither the First Officer nor I had been to Denver before so we were unfamiliar with the operations there. After landing in DEN we were given taxi instructions to the ramp. We did not know if there was a ramp frequency. We were using the EFBs and could not immediately find a ramp frequency. It was a very short taxi to the gate so we continued. After arriving at the gate and completing our checklists we investigated this further. We found on the second page of the airport diagram a box with ramp control frequencies. This box was obscured by the tools bar on the EFB. After finding this I called the Ramp Tower on the phone to discuss the situation. I explained what happened on our end and the person told me how the ramp procedures work in DEN. He said there was no harm done but they had noted the situation. 1) I should always be prepared especially when going into an unfamiliar airport. I should have tried to find this information before we landed in DEN. 2) Since I did not know this I should have asked Ground Control about a ramp frequency before continuing. 3) DEN GND should advise pilots to 'Contact Ramp Control' when giving taxi instructions to the ramp. 4) Put a note on the airport information page on the EFB about Ramp Control. 5) EFB adjustments. The plates can be very confusing (and not just on this plate but in general). I should have removed the removed the tool bar; but I didn't.