I am starting work on a new website project that is a website for a design agency and I want to understand how can I get to users? How to understand the target audience, so I can use research methods?
You should start by asking yourself who is the ideal user, customer and build on that. Are they business owners , what type of business would need a design agency ? If they are companies what type of person would hold a decision taking position inside the company ? etc. Ask Who they are, What they do, Why they do it , How they do it What they like etc.
Try to identify users that fit this profiles and try to interview them and start thinking of how their design problems can be solved.
The more specific and identifiable your target segment, the less time it will take to understand their needs. A quick gauge – can you think of at least 10 people who fit the profile you have in mind?
And you will probably need to do a few iterations of defining this audience and talking to them before you can really nail things down. You can read about the "jobs to be done" framework to give some structure to it.
And here's a resource on "How to understand customer needs?" that might help you out.