Hello, I just create a partner account to create a shopify website for my client who has already a wordpress institutional website, and a domain name that we want to keep. When I create the store in the partner account, what Store Name do I have to indicate (the only name of the brand is not available) ? Is storename.myshopify.com an url that have importance or just an URL for building the website (not a public url) ? Do we retrieve the URL with the domain name when we perform the migration?
Thank you very much for your help, it is my firt Shopify project 
The storename.myshopify.com URL is usually just for building. The vast majority of merchants use their own brand URL when they launch their store. You can build the store using that URL and then once you finish and are fully ready you can add the brand URL to the store. You would do that under Settings –> Domains and select Connect Existing
Thank you so much for your very quick response and these explanations!