Since you have set up your own domain and miiduu.com will never display in your store URL any longer, you cannot use miiduu's shared SSL certificate accordingly. You have to get one new SSL certificate. There are two ways to get one:
1. In System-> Own domain, buy an SSL certificate from us. Our tech team will do everything else for you. The cost is 99 US dollar a year. This is the way we highly recommend you to use.
2. You may also choose to buy SSL certificate from other websites, such as godaddy. After buying SSL certificate, you have to inform us of your store url and own domain. We'll generate csr file for you to get SSL certificate from the website you purchase SSL. Then email us your SSL certificate and we'll install it for you. The whole process is a little bit complicated.