Facebook ad settings for Link Clicks (CPC)

Background: I have Facebook page for a product. Advertisements for this product are handled separate Facebook Business Management account. I have done some advertising already on Facebook with over $10 budget that should unlock CPC. However, my ad draft seems to be charged still only by "impressions" and not "link clicks". Under "Optimization & Delivery" and "When You Get Charged" there are options for "Impressions" and "Link Clicks (CPC)" but the latter is always gray and has lock symbol preventing me to select it. Task: I will assign you as member to the products Facebook Business Management account. You will update the draft advertisement settings so that "When You Get Charged" will use "Link Clicks (CPC)". To my understanding this requires some sort settings for "Campaign Objectives" and possibly other sections too. These you can freely change to enable CPC charging.