What is the best methodology to handle database schema changes after an application has been deployed?

Hi,
VS2013, SQL Server 2012 Express LocalDB, EF 6.0, VB, desktop application with an end user database
What is a reliable method to follow when there is a schema change for an end user database used by a deployed application? In other words, each end user has their own private data, but the database needs to be expanded for additional features, etc.
I list here the steps it seems I must consider. If I've missed any, please also inform:
(1) From the first time the application is installed, it should have already moved all downloaded database files to a separate known location, most likely some sub-folder in <user>\App Data.
(2) When there's a schema change, the new database file(s) must also be moved into the location in item (1) above.
(3) The application must check to see if the new database file(s) have been loaded, and if not, transfer the data from the old database file(s) to the new database file(s).
(4) Then the application can operate using the new schema.
This may seem basic, but for those of us who haven't done it, it seems pretty complicated. Item (3) seems to be the operative issue for database schema changes. Existing user data needs to be preserved, but using the new schema. I'd like
to understand the various ways it can be done, if there are specific tools created to handle this process, and which method is considered best practice.
(1) Should we handle the transfer in a 'one-time use' application method, i.e. do it in application code.
(2) Should we handle the transfer using some type of 'one-time use' SQL query. If this is the best way, can you provide some guidance if there are different alternatives for how to perform this in SQL, and where to learn/see examples?
(3) Some other method?
Thanks.
Best Regards,
Alan

Hi Uri,
Thank you kindly for your response. Also thanks to Kalman Toth for showing the right forum for such questions.
To clarify the scenario, I did not mean to imply the end user 'owns' the schema. I was trying to communicate that in my scenario, an end user will have loaded their own private data into the database file originally delivered with the application.
If the schema needs to be updated for new application features, the end user's data will of course need to be preserved during the application upgrade if that upgrade includes a database schema change.
Although I listed step 3 as transferring the data, I should have made more clear I was trying to express my limited understanding of how this process "might work", since at the present time I am not an expert with this. I suspected my thinking
is limited and someone would correct me.
This is basically the reason for my post; I am hoping an expert can point me to what I need to learn about to handle database schema changes when application upgrades are deployed. For example, if an SQL script needs to be created and deployed
then I need to learn how to do that. What's the best practice, or most reliable/efficient way to make sure the end user's database is changed to the new schema after the upgraded application is deployed? Correct me if I'm wrong on this,
but updating the end user database will have to be handled totally within the deployment tool or the upgraded application when it first starts up.
If it makes a difference, I'll be deploying application upgrades initially using Click Once from Visual Studio, and eventually I may also use Windows Installer or Wix.
Again, thanks for your help.
Best Regards,
Alan

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