Multicrm and Saas (now it’s name is Landing Page) are a separate application and You should treat them as separate websites.
So you should install landing-page in your main website url. example: example.com and crm in subfolder app.example.com
You should know that multicrm and landing page are quite standard laravel applications (no surprises, custom weird thing etc).
Here are some guides about nginx – https://www.digitalocean.com/community/tutorials/how-to-deploy-a-laravel-application-with-nginx-on-ubuntu-16-04
PS. I published yesterday new 3.1.2 version with some bugfix and fixed docs. I suggest to download!
if you need anything let me know