change scheme name xcode

This is in the Xcode documentation available from the "Help" menu. Choose "Help" > "Xcode Help", then enter "rename scheme" to find it. Here are the steps:

Choose "Edit Scheme" from the "Product" menu.
Click on the "Manage Schemes…" button
Select the scheme whose name you wish to change
Press the "Return" key
It will select the name of the scheme and allow you to edit it.