How do I get 2 Dell monitors to work with my MacBook Pro (13-inch, 2017, Two Thunderbolt 3 ports)
If you want more than one monitor, you need to use two different connections, in your case Thunderbolt (Displayport) and some other connection, like HDMI or a dedicated Displayport connection. To do this you need a Thunderbolt 3 dock solution that supports this ability. There are many, such as Elgato, Belkin or CalDigit.

A recent (December 2018) Wirecutter review is a good place to start.