The whole system depends on honest answers. If you say yes to things you are not actually into, the results are meaningless. Here is how to make the most of it.
Answer for yourself right now. Not who you wish you were, not who you think the other person wants you to be, and not who you were five years ago. If you are curious about something but have not tried it, that is still a valid yes. If you used to be into something but are not anymore, that is a no.
Do not try to guess what the other person wants. The point is that neither of you knows what the other picked. If you start trying to game it -- saying yes to things you think they are into -- you defeat the purpose. The results will not reflect reality, and any conversation that follows will be built on a false foundation.
Saying no is fine. A no does not mean anything negative about you or the other person. It just means that particular thing is not something you are interested in right now. The other person will never know which specific questions you said no to.
Do not say yes to everything. Lykewise has tools to detect this. If you are answering a set someone created for you and you say yes to everything, there is a good chance they set test questions -- questions they said no to, specifically to catch people who are not being thoughtful. A test question warning will flag you as someone who might not be engaging honestly.
Take your time. There is no deadline. If a question makes you pause, sit with it. Come back later if you need to. Rushed answers are often less honest than considered ones.
Pay attention to the wording. There is a difference between "I am into this" and "I am curious about this." Lykewise questions are yes or no, so decide what yes means to you before you start. For most people, yes means "I am interested in exploring this" -- not "I have done this a hundred times."
Remember that the goal is useful information. A result that says you have three genuine shared interests is more valuable than one that says you have fifteen because someone was not being real. Quality over quantity.