New to the site and have little technical knowledge.
I have a mx andriod box and it has a custom logo on launch.
How can I remove this and have my custom logo on start up ?
You have to be rooted, but any boot animation changer can do this. Here is an example from the play store: https://play.google.com/store/apps/details?id=com.jrummy.apps.boot.animations
You won't be able to do this without being rooted. Lots of custom ROMs (custom Android OSs) will have this built in, or there are apps to do this as well.
The logo you are referring is known as
You can only change this if your phone's rooted.
After that you can change the logo by replacing
logo.bin from the system folder manually or your can flash any zip file through cwm/twrp custom recovery's.