Shopify set up and mailchimp

I am currently creating an online store to sell gym apparel, the clothing is currently getting made so I have no photos yet but would like my website up and running for them. I have started on the basics already; I have my inventory, I've made the SKU's, I have a simple layout. I would like help with; finishing the design of the website, customising the checkout, making sure the website is running correctly and help with MailChimp as I have set up automated emails but there is one I cannot get right.