If I may offer a bit of advice:
TL;DR training is easy. At most, you'll spend 20 hours a week on it - more likely closer to eight to 10. That's a small period during which you to have to get things right. Your nutrition is something you spend every waking hour 'doing': probably 85-110 hours a week. That's a long period of time, and you need to get at least 80% of it right 100% of the time.
Down the track it will be a major advantage if you make this a focus now. You're very, very light for your height and adding size will be down to diet. What that size is made up of (fat vs muscle) is also down to diet. Probably the biggest mistake I've seen beginners make is focusing on training over nutrition. You can train very well, but without good nutrition your efforts won't be well rewarded.
Learn how to eat, and how to eat a lot. It's pretty simple. Lean meat, lots of vegetables, carbs from rice and potatoes mostly (oats too if they agree with you), eggs, fish, olive oil, some nuts/nut butters. Always remember that most people your size eat much less than they think they do.
A good idea is to think in terms of mobility for purpose: figure out what you want to achieve, and make yourself mobile enough to do that. If you're a swimmer, for example, it is a complete and utter waste of time to become as mobile as a gymnast. If you're just looking to build a decent physique, there's no point in getting over-mobile. Squat to parallel or a bit below without weight and flat feet, fully extend your arms above your head, be able to touch your toes with straight legs. That will probably cover most of it.
As a rule of thumb, if you're spending over 10 minutes at either end of your training doing prehab, warmup and/or mobility, something is wrong with what you're doing. A great place to start is the Agile 8.
This last part take with a grain of salt, I guess, because it's more a personal opinion but something I've seen go hold reasonably true:
At some point you'll need to decide whether you're doing this for fun and to be active or to actually achieve a goal. Neither approach is wrong. The only thing wrong is if you aren't honest with yourself about what you want. If you want fun and activity, it really doesn't matter in the slightest what you do, as long as you enjoy it - but it will cost you dearly in results. If you want to achieve something, do what needs to be done. The goal doesn't care how you feel about what it takes to achieve it, just that those things are done. By all means be intelligent in your pursuit of your goal, but always bear in mind that the goal is the reason you are doing this. That means pain is endured, risks may be taken and hard choices may need to be made. It means consistency, patience and discipline are paramount. Forget motivation. Motivation is effectively useless. Take pleasure in the process instead.