i have an Icloud e-mail address but would like to change it, how can I do that?

Welcome to the Apple community.

Unfortunately you cannot change an iCloud mail address once you have created it. You can however use an iCloud alias which you can set up at iCloud.com.

To create an alias.....

Navigate to the Mail feature at iCloud.com and click on the gear icon in the bottom left corner. Choose Preferences from the drop down menu, then select accounts from the options across the top, here you can create your alias.