We simply cannot. It’s simply impossible. Other people can objectify us, but we cannot do it to ourselves. Let’s look at an example of this.
So, we have a woman. Let’s name her Julie*. Julie happens to think she’s sexy as hell. She’s a very self-confident woman and she loves her body. Julie sees an ad one day from some major outlet looking for women of varying sizes/races/disabilities to pose in their Thing. They want to show that all women are sexy. The point of the Thing is to be sexy. Julie says “I’m sexy as fuck! I’m gonna do this!” So Julie goes off and does the Thing and is generally sexy as shit.
So the Thing comes out, everyone sees it, and they say “Wow Julie! You were sexy as fuck in the Thing! Good job!” Now, according to some, since Julie posed in a Thing & was sexy & some men saw the Thing & thought she was sexy, Julie was “colluding in her own sexual objectification.” Does that make any sense?
In my book, that doesn’t make any sense whatsoever for a very specific reason. Julie saw the ad and made the choice to do the Thing with the explicit intention of being as sexy as she could. She knew people would find the images sexy and that was what she wanted. That was the intention of the Thing. Even if the purpose of Julie posing in the Thing was to be sexy, men and others can still objectify her. Once again, this is not her fault. She’s not “objectifying herself”. Other people are objectifying her.
Now, if the purpose for the Thing was something like an art reference, the situation might be different. If Julie had posed for a Thing whose intention was to give artists references on how to draw different types of bodies and there was no sexual intent or purpose behind any of the images, but someone took the images and posted them on a sexual website or wrote an article using said images talking about how amazing Julie’s tits looked or rated the women on how fuckable they were, that would be objectification.
In that case too, it is not Julie’s fault she was objectified. If you want to blame anyone, blame the people doing the objectifying.