First, you need to download Skype onto your device. The next step is to create an account, if you do not already have one.
Once you have used your account to sign in to Skype on your device, the next step is to add some contacts. See my earlier answer in this post for tips on how to do that.
Once you have a few contacts, it is time for you to start calling, sending messages or sharing files and screens. If you are having trouble finding your way around Skype, you have to search in skype support.