It's a funny way to use the word "lock". I guess advertisers are always trying to come up with interesting and "catchy" ways to use language. To "lock" means to "fasten or secure something (with a lock)". So you can lock a door, or the drawer of your desk. Or you can lock your bicycle to a tree. The word gives you this feeling of "securing something" so it can't be taken away. I've never worn makeup, but I imagine it doesn't stay perfectly in place for a very long time. What happens to lipstick when you have dinner? What happens to eye-shadow when you watch a sad movie and start to cry? I bet makeup only feels perfect during the first few minutes, after that it begins to deteriorate. Wouldn't it be nice if you could make your makeup PERFECT and then "lock" your face so nothing changes? So that's what that phrase means in the context of that advertisement. They are saying "our products are very high quality and our makeup will stay perfectly on your face during the entire evening".

Hello Elena! I am sorry but I am unable to access the link. Could you perhaps explain the context and then I could try to explain it? I would love to help!

Thank you Paul! That's what I was thinking, but wanted to make sure. :)

It means to have something under control. In this context, it is referring to a woman being in charge of her face and choosing how she wants to represent herself. She has the face that she wants "on lock." It is common urban slang being used here as a marketing tool.