How to upgrade canister and recovery data

Hey guys, I’ve been bothering by this question for nearly two weeks: I use ‘canister-tools’ built by @levi ,I have to say it’s a great library, but I don’t know how to use it. I change some fields in a structure, but when I want to deploy backend it shows that the change will make ‘BREAKING CHANGE’ to my project,and then I click ‘yes’ the whole old data is totally cleaned,I also use the snapshot, create snapshot and download it, and then append and load it, but still don’t work. Anybody who have used it before can tell me how to use it? Thanks a lot!