How to add sign up form at the end of post like it is in Casper theme

[Transylvania]

I switched to ruby theme from default Casper theme but ruby theme has no sign up for more like this form at end of post like Casper.
How can I add one at the end of post in ruby theme.
I am newbie to ghost and I have no experience with coding and stuff.

[brightthemes]

Here is the code from Casper for that section:

TryGhost/Casper/blob/main/post.hbs#L85-L100

You could integrate that into the post.hbs in your Ruby theme.