If you've previously signed in and customized My Yahoo!, most likely you just need to sign in again. Go to the Sign-in page and click Sign In.
It's also possible to view and customize My Yahoo! when you are not signed in to your Yahoo! account. Any customizations you make when you are signed out do not carry over when you sign in. They may reappear when you sign out again, or they may be lost when you change your browser settings. If you make sure that you are signed in before customizing your My Yahoo! page, you'll always be able to see your customizations when you sign in.
Tip: We've provided a Keep Me Signed In checkbox on the Sign-in page so that you won't have to sign in each time you come back. Checking this box keeps you signed in for up to 2 weeks, so if you're sharing your computer you won't want to do this, but if you are the only one using your computer, it's a great convenience. If this box is left unchecked you'll have to re-enter your password more frequently, but the chance of someone else accessing your account through your computer is reduced.
If the issue you're having isn't related to being signed in or out, use the Contact Customer Care button on this page to get further assistance.