Walk Behind Lawn Mowers

I just purchased a model 961450022 AWD mower. I got it all put together and tried to mow and it takes off way to fast for me. I know there is that cable adjustment to make it more aggressive but how can I slow it down? I noticed too that adjustment can't easily be made by hand. Do you use small wrenches on it. That thing is going to cause me some damage if I can't slow it down. Thank you

Virgil Walden