If you're wanting to grow your email list, you need to offer your audience something of value in exchange for their email address. Why should the prospective buyer be interested in hearing from you? Do you have exclusive offers for your email list? For example, a limited edition product, or new season items they may be keen to get their hands on? Nobody wants to be spammed, but most of us appreciate a valuable offer. Make sure you have a reason for your audience to sign up to hear more from you and you'll find your email list grows.
Note: you must obtain consent from subscribers before adding them to your email list, or you may find any email that comes from your company, is marked as spam.