How to Customize ToolBox UI in iOS sdk

I am developing a video conference application in ios , using jitsi how to customize the toolbox UI , like changing it size adding layers like corner radius , background color change .
I can’t find the files in framwork where to change UI.

All the ui code is under this package jitsi-meet/react at master · jitsi/jitsi-meet · GitHub
For example the native implmentation of the toolbox is here jitsi-meet/react/features/toolbox/components/native at master · jitsi/jitsi-meet · GitHub

Thanks for the reply

How to work with these files.
How to add these files to my xcode project.

If you are trying to create a UIToolBar programmatically, you can’t just set a frame without allocating and initializing the toolBar. Try this:

myOwnToolBar = [[UIToolBar alloc] initWithFrame:CGRectMake(0, 0, 100, 44)];
[self.view addSubview:myOwnToolBar];

When you create an IBOutlet, an alloc/init call is implied. You just need to keep in mind that this is not true for objects created in code.