Pop up on home page

Hello!
Thanks for a fab theme.

I’d like to put a pop-up on my homepage which includes a link to a YouTube video. At a later date I’d like to change the content of the pop up to, for example, invite mailing list sign-ups or highlight offers.

I’ve seen that some plugins can mess up the website due to conflicting code etc. So, do you have any thoughts on the best way for me to add a pop-up?

Thanks so much,

Kate