Hey, i am making a small project about a relay and a push button using one button library , i wanted to use the millis function as when i press the button once, the relay starts blinking and when i press the button twice the relay stops.
Any help would be appreciated.
Show us where you got the library from and your code that you're working on right now. What does the code actually do? What do you want it to do different?
There are a few "one button" libraries, this could be the 'one' 
GitHub - mathertel/OneButton: An Arduino library for using a single button for multiple purpose input..
It uses millis() itself to determine if a button is pressed once, twice or for a long time.
You can use that library and also use millis() in your sketch as well. That is no problem.