How do I actually go about valuing companies?

I have knowledge in undergraduate finance and I’ve learnt a lot of valuations of companies, but how do I actually go about doing this in real life? For example the discounted cash flow model – where do I go about finding expected cash flows?

And say I calculate expected value of the company then and I compare it to the EV of the firm’s financials from online – aren’t those values often outdated and from previous quarters?

TLDR: I have no clue how to turn theory into practice in fundamental analysis and would like some tips and help please