A user might want to sign-in using another account for a few reasons. Like if you have purchased an app using another account than the one being used currently then you need to sign into another account in order to re-install the app.
In order for you to sign into Window’s store using a different account you need to sign out first and then sign in using the other account.
Sign in to Windows Store using a different Microsoft account in Windows 10
IMPORTANT: If you’re using a local account (an account other than Microsoft account), please carefully read the instructions in Step 6 to avoid automatically migrating your local account to Microsoft account.
Step 1: The first step is to open the Store app. There are multiple ways to launch it like typing it in the start menu search bar or launching it from its source etc.
Step 2: Now click on your account picture on the top of the screen and tap on your e-mail address, this will take you to your account dialogue.
Step 3: Now click or tap on the e-mail currently being used, this will show a sign out option, use this to sign out from the store and this account. You can now sign into store using another account.
Step 4: Now click on the user icon on the top right next to the search box and tap sign in.
Step 5: A list will be shown of all the accounts you have used to sign in. Click on any of those or use a new one.
If you select one of the previously used accounts you will be asked for the password, if you select Microsoft account option you will need to enter e-mail address as well.
Step 6: Once you enter the password, if you’re using a local account instead of a Microsoft account in Windows 10, you will see the following screen. Please DON’T enter your local account password if you plan to sign in to Windows 10 without using a Microsoft account.
Simply click or tap Sign in to just this app instead to sign in to only Windows Store using Microsoft account. Entering your password will automatically convert your local account into Microsoft account.