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Other than the correct cable to connect the monitor to the computer there is nothing else you need to run dual display (two monitors) on your HP Envy 700!
Here is a picture of the back of an HP ENVY 700-149 which came with an add-in graphics card (NVIDIA GeForce GT 635) which has a single HDMI port and a combo DVI port with analog VGA output (using a DVI to VGA adapter).
To run dual display you would connect one monitor to the DVI port and one monitor to the HDMI port. You can get adapter cables to convert between connectors. Say for example you have two monitors and each of them only has DVI input ports, you can get a HDMI to DVI cable to connect that monitor to the HDMI port.
If your HP Envy 700 doesn't have an add-in graphics card or has a different graphics card then the one I listed then you might have a different number and layout of ports. Feel free to update your question with the exact model number or the model number of the graphics card in computer and we can provide a more exact answer but pretty much any configuration of HP Envy 700 supports dual monitors.
If after you connect your second monitor it's not displaying how you would like press Windows Key and P at the same time and it will open all the secondary display options in Windows 10 (mirror display, stretch/extend display, secondary desktop). If you want to remove the start button/taskbar from the secondary monitor rick click on the taskbar and click on properties. Scroll down to "show taskbar on all displays" and set it to off.
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