I have just gone through this and it was a bit of a bitch to get through tbh. But let me try and explain what I did.
First you need to understand that Amazon ACM only works with a number of services.
The following is a list of services that ACM supports. 
So if you want ACM integration, you can choose any of the supported services like ELB/CloudFront etc. in front of your EC2 instance and integrate the SSL/TLS certificate requested from ACM during their setup. The following link  will guide you through an example to create an HTTPS/SSL load balancer using the Console and register your EC2 instances with the same which will establish an HTTPS connection between the ELB and the internet on behalf of your EC2 instance.
Please be aware that your ELB needs to have a healthy pings to your EC2 instance - if it does not get the healthy pings, it will not route the traffic there, read more here:
Once I got everything done above, I went into my prestashop admin and changed the shop URL from the IP to my SSL URL (https://yoururl.here)
I then navigated to this file:
And did a search replace on the IP to the domain. (do a backup first of course!)
This fixed it for me.