Install SSL form Let's Incrept

How can I Install SSL form Let’s Incrept?

You can’t install ssl from LE here… Besides you need root chain to make your website trusted by almost all browsers!
You should just use Cloudflares ssl as it well complete ur ssl chain without doing anything!

I don’t use Cloudflares By the way cause it broke my email client side and also my dns that I mx record will not work which is bad…
U can see my domain here that I’m not using cloudflare:

Well! I’m seeing you’ve also installed Let’s Encrypt SSL, can you tell me step’s for doing it. I don’t like to install Cloudflare or Comodo (installed for main domain}

I want to install for subdomain…

Ah sure!
Just choose the txt file verification and upload it to your root folder (htdocs) and upload it on .well-known/acme-challenge and wait at least 2-3 mins. (I don’t know but I just wait 2-3 minutes) and then pressed the download ssl and it will generate your ssl successfully!

You can use between this web LE acme client:

Let’s Encrypt cannot be used on InfinityFree yet: