How to enable external display on touchbar MBP with broken screen
There is two solutions that I can recommend for you. 

First, a very generic one where you need to close the screen lid. 


Hook the LCD display to the Mac with the appropriate adapter
Hook up the external keyboard and mouse (optional but recommended)
Boot the MacBook with the broken screen, then close the screen during boot


This will automatically boot your Mac to use the attached external screen

In brief: Restart your system and then close the lid so the lid sensor acknowledges the lid is closed your external display should automatically become the primary display.

And, Second, if you have another Macbook with you, you can try this crazy idea too

If you have easy access to a second Mac and the right cable to connect the two (e.g., Thunderbolt to Thunderbolt, USB-C to Thunderbolt, USB-C to USB-C, etc.), you could:


Connect the two Macs with said cable
Put your damaged MacBook Pro into Target Disk Mode by holding down its "T" key while you turn it on
Turn on the second Mac while holding down its Option key so you get to choose which partition to boot from
Choose the system volume of the broken MacBook Pro


This basically lets you use the intact second Mac to boot into the system that is installed on the MacBook Pro with the damaged screen. If there are indeed any software or hard drive issues with that first Mac that prevented you from logging in, you are now able to see and potentially address them.

For more details on Target Disk Mode, see this guide.