Please kindly use the search-bar on the forum to get the solution for your problem as there are been said what signing is in many places on this forum.
Easy said: your phone has an imei number. yes, I'm not lying
press *#06# on your standby screen and your imei number will pop-up. An unsigned application as rotate me and nokmote are not signed. to make them work you have to make a certificate for your phone containing your imei number though. If you are desperate to learn then please use google. if you want something to be signed search for the signing thread on this forum and follow the rules there to get anything signed. If you want a tutorial it is to be located in the master zone which you have to read the rules and do as following to enter the zone.