Открывание Dialog

Ваша задача может выглядеть примерно так:

import sys
from PyQt5 import QtCore, QtGui, QtWidgets
from PyQt5.Qt import *


class Ui_Dialog(object):
    def setupUi(self, Dialog):
        Dialog.setObjectName("Dialog")
        Dialog.resize(429, 300)
        self.pushButton_2 = QtWidgets.QPushButton(Dialog)
        self.pushButton_2.setGeometry(QtCore.QRect(170, 230, 75, 23))
        self.pushButton_2.setObjectName("pushButton_2")
        self.toolButton = QtWidgets.QToolButton(Dialog)
        self.toolButton.setGeometry(QtCore.QRect(0, 280, 61, 19))
        self.toolButton.setObjectName("toolButton")
        self.progressBar = QtWidgets.QProgressBar(Dialog)
        self.progressBar.setGeometry(QtCore.QRect(10, 10, 421, 23))
        self.progressBar.setProperty("value", 24)
        self.progressBar.setObjectName("progressBar")
        self.lineEdit = QtWidgets.QLineEdit(Dialog)
        self.lineEdit.setGeometry(QtCore.QRect(10, 40, 411, 20))
        self.lineEdit.setObjectName("lineEdit")
        self.lineEdit_2 = QtWidgets.QLineEdit(Dialog)
        self.lineEdit_2.setGeometry(QtCore.QRect(10, 70, 411, 20))
        self.lineEdit_2.setObjectName("lineEdit_2")
        self.lineEdit_3 = QtWidgets.QLineEdit(Dialog)
        self.lineEdit_3.setGeometry(QtCore.QRect(10, 160, 411, 20))
        self.lineEdit_3.setObjectName("lineEdit_3")
        self.lineEdit_4 = QtWidgets.QLineEdit(Dialog)
        self.lineEdit_4.setGeometry(QtCore.QRect(10, 100, 411, 20))
        self.lineEdit_4.setObjectName("lineEdit_4")
        self.lineEdit_5 = QtWidgets.QLineEdit(Dialog)
        self.lineEdit_5.setGeometry(QtCore.QRect(10, 130, 411, 20))
        self.lineEdit_5.setObjectName("lineEdit_5")

        self.retranslateUi(Dialog)
        QtCore.QMetaObject.connectSlotsByName(Dialog)

    def retranslateUi(self, Dialog):
        _translate = QtCore.QCoreApplication.translate
        Dialog.setWindowTitle(_translate("Dialog", "Dialog"))
        self.pushButton_2.setText(_translate("Dialog", "Майнить"))
        self.toolButton.setText(_translate("Dialog", "Настройки"))
        self.lineEdit.setText(_translate("Dialog", "Привет,это моя игра \"Мамкин майнер\" одним словом,это кликер."))
        self.lineEdit_2.setText(_translate("Dialog", "Что-бы начать \"Майнить\" нажмите кнопку \" Майнить\" да это звучит глупо."))
        self.lineEdit_3.setText(_translate("Dialog", "Версия игры-V.1"))
        self.lineEdit_4.setText(_translate("Dialog", "Возле кнопки \"Майнить\" есть кнопка \"Настройка\"Там можно изменить сложно-"))
        self.lineEdit_5.setText(_translate("Dialog", "сть.Игра была написана на Python,код прогресс бара и кнопки.Был украден с stackowerflow :3" ))


class Dialog(QDialog):
    def __init__(self, parent=None):
        super(Dialog, self).__init__(parent)  
        self.setWindowTitle('Dialog')
        
        self.lineEdit = QLineEdit()
        self.btn = QPushButton("Button")
        
        self.vLayout = QVBoxLayout(self)
        self.vLayout.addWidget(self.lineEdit)
        self.vLayout.addWidget(self.btn)
        

class MainForm(QDialog, Ui_Dialog):
    def __init__(self):
        super(MainForm, self).__init__()
        self.setupUi(self)
        self.pushButton_2.clicked.connect(self.clickButton)
        
    def clickButton(self):
        self.dialog = Dialog(self)
        self.dialog.show()
        
        
if __name__ == "__main__":
    app = QtWidgets.QApplication(sys.argv)
    w = MainForm() 
    w.show()    
    sys.exit(app.exec_())