Thanks for the replies. I do have the setupUi(this) in the constructor.

inputs::inputs(QWidget *parent) :QWidget(parent), ui(new Ui::inputs)
{
ui->setupUi(this);
}

In the mainWidget constructor , I do
in=new inputs(this);
QHBoxLayout *lh= new QHBoxLayout;
lv->addWidget(logo);
lh->addWidget(in);

But nothing shows on the screen. Is there something else needed?
Thanks.