Left side menu, doesnt have clay, just brushes, im using blender 4.3

Clay is in the asset shelf at the bottom of the window in 4.3. If you don't see the asset shelf then click view and check asset shelf. If you have default keymap then you can use shift+Space to access the brushes. You can also click the brush dropdown in the tools setting. Tools settings can be found in 3 places.

1. Right below the header if show tool settings is checked under view. Brush dropdown is the first thing on it. 
2. The tools tab of the n-panel(Sidebar). The Brush dropdown is the big brush icon.
3. The Active Tools and workspace tab in the Properties editor. Again the big brush icon.