You'll need to enumerate through the windows and match the title of the window to get the one you want. The code below searches for a window with "firefox" in the title and sets the focus:
import win32gui
toplist = []
winlist = []
def enum_callback(hwnd, results):
winlist.append((hwnd, win32gui.GetWindowText(hwnd)))
win32gui.EnumWindows(enum_callback, toplist)
firefox = [(hwnd, title) for hwnd, title in winlist if 'firefox' in title.lower()]
# just grab the first window that matches
firefox = firefox[0]
# use the window handle to set focus
win32gui.SetForegroundWindow(firefox[0])
To minimize the window, the following line:
import win32con
win32gui.ShowWindow(firefox[0], win32con.SW_MINIMIZE)