Can I get some help please?

The easiest way (and safest) to age up a sim I've found is without cheats. For the baby, all you have to do is click on it, then chose age up. For anyone else, just cook a cake, put the candles on it, then have them blow out the candles. You can keep putting candles on the cake and have sims blow them out as many times as you want. Aging up each time. The reason I say it's 'safe', is because I've noticed many times in CAS using full edit mode that aging them up there can break the genealogy tree. Aging down sometimes does that too. The only way I know of to age down is with the cheat. You can buy a potion with reward points to reset whatever age they are currently at (without cheats, unless you cheat to give them more reward points). But that's another story.