Capital can be in many forms. The time that you will spend to learn and grow your business is one of your main capital, even though no monetary capital but you need to invest human capital in your business. Each individual's time is precious, including you. The time that you will spend on growing your business is the time that you will spend less on other things such as leisure, family, academics.
I think what he means is capital in the form of money. Even though we have in-depth knowledge in a field, we cannot run it and develop it without capital. However, I think all of that can be done, even without capital. There are many things to do when we don't have capital, but want to run a business. Well, the first suggestion is to get a job, and that's a common thing. Another is looking for capital by selling skills, this can happen at the same time when you run a business without capital, but by selling the skills you have. And the other is looking for investors. Yes, there are many people out there who want to grow their money into more, but they don't have ideas, or are lazy about running a business. So, you just need to look for and come to them, bring a proposal, and pray that your request is accepted.