Drop shadow to generate blocks buttons

.gb-button {
            -webkit-box-shadow: 0px 0px 13px 0px #000000; 
            box-shadow: 0px 0px 13px 0px #000000;
}

Go to Appearance > Customize > Additional CSS and paste the above code. I think this should work.

Thanks Suraj,

worth using an RBGA value to give you better control over the color - for example a subtle shadow below:

.gb-button {
    box-shadow: 0px 8px 24px -8px rgba(0, 0, 0, 0.7);
    -webkit-box-shadow: 0px 8px 24px -8px rgba(0, 0, 0, 0.7);
}

OR you can add it like so to make the shadow appear on hover:

.gb-button {
    box-shadow: 0px 8px 24px -8px rgba(0, 0, 0, 0);
    -webkit-box-shadow:  0px 8px 24px -8px rgba(0, 0, 0, 0);
}
.gb-button:hover {
    box-shadow: 0px 8px 24px -8px rgba(0, 0, 0, 0.7);
    -webkit-box-shadow: 0px 8px 24px -8px rgba(0, 0, 0, 0.7);
}

Thanks Suraj and David.It's working.

👍👍