Using byoip address with a Lightsail instance?

I'm trying to attach one of our BYOIP ip addresses to a Lightsail instance. Can someone tell me how to do this? I asked Amazon Q if this was possible and got the following answer:

Yes, you can assign a BYOIP IP address to a Lightsail instance. Here are the basic steps:

1. Create a static IP in Lightsail and attach it to your instance. This will prevent the public IP from changing when stopping and starting the instance.

2. Create a BYOIP address range in your AWS account and associate it with your VPC.

3. Allocate an address from your BYOIP range.

4. Modify the route table associated with your Lightsail instance to route traffic for the BYOIP address to the instance.

5. Update any DNS records like your domain name to point to the new BYOIP address instead of the Lightsail public IP.

It involves a few additional configuration steps compared to just using a Lightsail static IP, but it allows you to use an IP address from your own pool. The AWS documentation has more detailed instructions on setting up BYOIP and routing traffic to resources like Lightsail instances. Let me know if any part of the process needs more clarification.

I'm stuck at the modify the route table part. I can start to add a new route for one IP address from my range, but when I select to route to an Instance and enter the i-<number> instance id of the Lightsail instance it says it doesn't exist.