On the menu bar of the Skype window when you have logged on, click on contacts, then Add Contact. Enter your frienjd's email address, add a message saying something like "Hi this is gordiescotland1. Would you add me as a contact" and send it.
Once your friend has added you as a contact, they will appear on the left hand side of the Skype thing as a contact. To talk to them click on their name and the right hand side of the screen will change from all advertising to mostly blank with a text entry box at the bottom.
If you want to chat using text only, use that box to send messages - the sent and received messages will show above the text box.
At the top of the right hand side of the window is a bar with three icons oon it - a camera, a phone and one where you can add people. To start a video chat with your friend, click on the camera icon.
So far so good and all free.
Clicking on the telephone icon allows you to make a phone call to your contact via Skype, but you may need credit to do so if it is a real telephone or mobile your friend is on at the time. If your contact is on line and on a computer, clicking the phone icon will connect tou so you can have a voice conversation, again for free.