You can join ShareASale by visiting their website. You need to create an account by filling out the sign-up form. The form asks for basic details like your name and email address. You will also need to provide your website or blog URL. ShareASale will ask you to choose the types of products you want to promote. You should review their terms and conditions before submitting your application. After applying, ShareASale will review your site and approve or deny your application. Once approved, you can start joining affiliate programs and promoting products to earn commissions.