You can choose one of three settings for the extent to which your content is made public: Make My Content Public, Make My pixiv public, and Private. If you select "Make My Content Public", your content will be displayed in search results.
Make My Content Public: Your content will be made public to all users.
Make My pixiv Content Public: Content will only be made public to people who are added to your My pixiv page. (What is My pixiv?)
Private: Your content will not be made public. Only you will be able to see your content.