How can I fix purchase pathway issues and test POS system on my e-commerce site?

I’ve set up my Shopify site (www.crystillery.com) and it looks pretty good and works pretty well but I am now looking for some help to fine tune it and test and debug. I am now testing the purchase pathway and it tells me I can’t buy because I can’t ship to me. How do I fix this? I then want to know how to test the POS payment system for when I sell at markets. I tried to turn on international markets but it doesn’t seem to be working and I need to know what I’m doing wrong here. After this, I want to know how to add text that appears when you hover over buttons, what the “buy now” button is and how to use it, how to make pictures link to a section of the site and a few other things. For now, I need to fix my site so my customers can buy and I have a customer currently trying to make a purchase. Where do I start? Is there someone I can pay for some support? Thank you