There should be an option under 'settings' to control this.
But a bit more info would help.
Are you using internet explorer, firefox or chrome?
Have you perhaps got google as your internet home page - and if so the 'safe search' is one of the settings in google, alter it by going to 'settings' at bottom right
By all means follow the link given by Buenchico. However, he may agree with me that you can ignore Steps 3 & 5. of the printed steps for removing 'safesearch'.
Instead, it should be sufficient to do a scan with whatever AV programme you have in your computer, along with a 'run through' of Malwarebytes; rather than going along with steps 3 & 5.