Import and link external proxy

Hey everyone,

Sorry for my 'bad' english ! 😛

I'm going to full 4K !!!!

let's go for 3 weeks rendering 😄

And i have 2 question:

1. I know we can make proxy directly from after effects but if i want to make it from another program (media encoder, hanbrake...) and i want to import it to after effect,

How to link it to the original vidéo for export render ?
Waht is settings for make it sure for woking ?

2. (maybe is the same solution)
I record with my s5iix now and i have 2 tracks: the original and the proxy,

How i can tel to after effects, this is a proxy and this is the orignal footage

Thanks !
love you