Here is my code to implement and change to label side in top of frame....
def login():
global login_screen
login_screen = t.Toplevel(main_screen)
login_screen.title("Login")
login_screen.configure(background="lightpink2")
login_screen.geometry("700x750+600+200")
frame=t.Frame(login_screen,bg='pink',pady=150,padx=100)
l=t.Label(frame, text="Please enter details below to login", bg="deeppink4", fg="white",width="50", height="2", font=("Calibri 16 bold", 13))
l.grid(row=0,column=0,columnspan=2,padx=5,pady=5,ipady=5)
#t.Label(login_screen, text="").pack()
global username_verify
global password_verify
global mobile_verify
username_verify = t.StringVar()
password_verify = t.StringVar()
mobile_verify=t.StringVar()
global username_login_entry
global password_login_entry
global mobile_login_entry
t.Label(frame, text="Username * ").grid(row=1,column=0)
username_login_entry = t.Entry(frame, textvariable=username_verify)
username_login_entry.grid(row=1,column=1,pady=5)
#t.Label(login_screen, text="")
t.Label(frame, text="Password * ").grid(row=2,column=0)
password_login_entry = t.Entry(frame, textvariable=password_verify, show= '*')
password_login_entry.grid(row=2,column=1,pady=5)
#t.Label(login_screen, text="").pack()
t.Label(frame,text="Mobile number *").grid(row=3,column=0)
mobile_login_entry=t.Entry(frame,textvariable=mobile_verify)
mobile_login_entry.grid(row=3,column=1,pady=5)
#t.Label(login_screen,text="").pack()
t.Button(frame, text="Login", width=10, height=1, command = login_verify).grid(row=4,column=0,columnspan=2,padx=10,pady=5)
frame.pack(side="bottom",pady=200)