Using freelance platforms can be good for some but not others, especially when using the ones that make you pay a fee to get clients or take a percentage of your earnings. These can be a race to the bottom as you compete with those who can afford to lower their prices. There have also been cases where those sites will not allow you to sign up citing lack of experience or ban your account for any number of reasons. If you do decide to join a pay-to-use freelance platform read up on how others have successfully navigated them to avoid common mistakes.
Cold emailing is a way to find clients/work, though they can have a low rate of return as a lot of people don’t appreciate or read an email from someone they don’t know. This is one of those ‘throw as many as you can and see what sticks’ approach to finding clients. Try creating different styles of emails to send to see which works best and always personalise them to the company/person you are sending them to.
You can also search for and ask web design/development agencies in your area if they have an overflow of work and are willing to work with freelancers. If you would like to move into a permanent position then searching for web design/development agencies vacancy/career pages can be useful to find jobs that aren’t on any recruitment sites. Plus your CV is more likely to be read than discarded by a recruiter or algorithm.