If you are seeing this message ‘first time signing in from here’ then you do not need to worry. Since yahoo is always looking for the safety and security of their users. When you try to sign in from a device that user does not recognize, you will be asked to enter a code when you send it to your phone or email so that yahoo can confirm that it is really you. When you find this message, you need to choose whether you want to verify using the phone or the alternate email address. For the extra security, yahoo might ask to change the password if necessary. To know more on yahoo security options, call us at Yahoo customer support phone number 1-800-407-7258.