Hi, everyone. This is my first message in LingQ, I’m a Chinese who is interested in learing English very much. Also, if there is anyone that have any questions about Chinese or wanna know something about China, I can help you,too. Here is an idiom I don’t really understand, I need some help. “with sth to spare”
eg. I had as much flour as I needed with something to spare.
Fred said he should have enough cash to last the week–with money to spare.
I hope that native speakers can tell me how to use it. Thank you very much! 
I hope I’m understanding you correctly. But, when someone says:
“With something/some to spare”, they are saying that they have stuff/something that hadn’t been used, or something "left over. In other words, something to spare describes you having some more of that “stuff” to use that wasn’t already used.
So, with Fred, he had enough money that week, but still has some left over, to use later.
Thank you for your explaining!