You are probably not an expert in all things related to your project, for example, ICO, blockchains, whitepaper, lawyers, commerce, finance, marketing, etc. Here's where an adviser can come in handy - they're usually guys who have experience in launching blockchain projects and are ready to share their knowledge with you, give an advice, answer questions, and so on. For a certain reward on your part.
Look at the most blockchain projects - as a rule, they have several advisers. Usually, all advisers are listed on the project page with key information about each of them, for example, the field in which they are most knowledgeable. The more experts there are in a team, the more confidence it causes. Especially if they are really experienced advisers who have participated in successful projects in the past.
How to pick the right one? You can find them personally at conferences, meetings and events dedicated to blockchain. Just communicate with other teams, with crypto enthusiasts, ask for their advice, ask about good advisers who will be interested in work with you, tell about your project at such events so that such experts and enthusiasts could find you themselves and suggest their help.
You can also look for them offline. Surf bitcointalk and similar forums, surf blockchain projects and pay attention on their advisers, remember, whose project is successful, write to these experts and ask for cooperation. As a rule, they are open to communication. Of course, your project must be look reliable and promising.