Centering and adding a push button to a grid window, TKinter

[menator01]

Your code altered a little. Expands with the window

import tkinter as tk

aList = ["Bin 1", "Bin 2", "Bin 3", "Bin 4", "Bin 5","Bin 6", "Bin 7", "Bin 8", "Bin 9", "Bin 10", "Bin 11",
        "Bin 12", "Bin 13", "Bin 14", "Bin 15"]

root = tk.Tk()
root['padx'] = 5
root['pady'] = 5
root.title('Feed Bins')

root.columnconfigure(0, weight=1)
root.rowconfigure(0, weight=1)

frame = tk.Frame(root)
frame['highlightbackground'] = 'black'
frame['highlightcolor'] = 'black'
frame['highlightthickness'] = 1
frame.grid(column=0, row=0, sticky='news', padx=5, pady=5)

for x in range(5):
    frame.grid_rowconfigure(x, weight=3, uniform='rows')
    for y in range(3):
        frame.grid_columnconfigure(y, weight=3, uniform='cols')
        label = tk.Label(frame, text=aList[x+(y*5)], relief='raised', font=(None, 16, 'bold'))
        label['bg'] = 'red' if aList[x+(y*5)] in ['Bin 3', 'Bin 12', 'Bin 14'] else 'gray86'
        label.grid(column=y, row=x, sticky='news', padx=5, pady=5)


btn = tk.Button(root, text='Button', font=(None, 14, 'bold'))
btn.grid(column=0, row=1)

root.mainloop()