Password manager
If you choose a separate, secure password for each service, you have a lot to remember. Password managers assist in remembering and creating secure passwords. They store a virtually unlimited number of passwords in a secure password database. They also provide an easy way to generate strong passwords via built-in password generators. There are some free and good password managers, for example KeePass.
Read why you should use password managers on the page about password manager. There you will also find insctructions on how to install KeePass step by step instruction.
