I've had several instances in my life where I've been alone for extended periods of time, almost at the same age you are now. I've generally enjoyed it, but not sure what the "How To" is for being alone. For me I've used my alone time to do new/learn things. I taught myself parkour, went and did Brazilian jiujitsu for years, did painting/art classes, went indoor rock climbing, read a lot more on philosophy, went to philosophy groups, joined my local humanist/secular society, worked out a lot more and went running, worked on my own programming projects, geocached, went to local lectures/presentations, all kinds of things. Basically I just followed any random thing my brain thought was interesting. As a side effect I ended up meeting a lot more people than I would have otherwise. I remember feeling anxious when I first became alone but I focused on the fact that I had a lot of freedom. Once you start experiencing your own freedom it feels good! It took a bit, I remember I felt mentally shackled about what I could do, but as I did things I just found there was more that I wanted to do.