Brief Answer:
follow the advises.. maintain a healthy lifestyle..

Detailed Answer:
Hello XXXXXXX Welcome to HCM,

I've gone through your query and understand your concern,

Bad cholesterols are bad because they make the body prone to develop Coronary artery diseases in the long term..so it's always appreciated active concern for keeping them down..

First and foremost thing is dietary changes, avoidance of junk/ pre-processed/ deep fried/ excessive sugary/ carbohydrate rich foods..

Changing the daily wheat/flour containing items to whole-wheat/whole grain foods..

Include fresh green vegetables, limit red meat intake instead try lean protein like chicken and fish in daily diet..

Having healthy snacking options like roasted/baked muesli, almonds-ground nuts, fresh fruits instead of deep fried junk foods..

Avoiding smoking and alcohol as much as possible..drinking a lot of water and staying well hydrated..

Diet alone won't be suffice, as there's a need of working out - daily 30-40 min of active working out is extremely important..

All these being said, there's a certain extent to which they can control to keep the bad cholesterols in the body(varies from person to person- BMI, overall body metabolism , associated co-morbidities and several other variable factors), so when it's out of proportion, there's a need to get clinically checked up by a physician in order to get the most effective management for future well being..

Let me know if there's any further queries..

Take Care
Kind Regards

---