Making sure everyone in the team participates in the creative process is a hard task. We are not only dealing with different personalities, but there are also many factors that could make some people quiet and others too loud.

There are two useful things you could do to level all the voices.

Ask the quiet ones
Never tell someone to shut up, even when they keep monopolising the conversation. Instead, try to direct your questions to the quiet ones.  Use sentences like "I'm interested in hearing everyone's opinions, Jessica, what do you think about this,?".

It's essential to be aware of the space everyone takes on the conversation. Redistribute the times to make it evener. But, remember, it's not about having all the members to talk about the same amount of time, it's about hearing all the voices.

Use inclusive methods
Prepare participatory before your sessions. For example: Ask everyone to note down their ideas/reflections/opinions on post-its before you start sharing. In that way, you'll give your team some time to think before they talk. It will also naturally create turns for everyone to share and speak up.