This is something that leaders have to do.
They have to take the initiative, make things happen and take responsibility for driving the business forward. Even if you are not in a management role, you can act like a leader and take action. Make decisions that are in the best interest of your business and put yourself forward for work that will get you noticed (sometimes that means taking on tasks that nobody else wants to do.)
Ask for feedback
During your one to one meetings with your Executive (that are about your personal development), you should really ask for input on the skills that make you a leader, such as taking the initiative, understanding the way the business works, motivating others, taking responsibility for your work and the success of the business.
There are many leadership skills that you can acquire, and it would be good to get feedback on what areas you can improve. If you work with teams or project groups, you should also ask for feedback after the project is finished.
Have those difficult conversations
Difficult conversations are obviously always hard to have, but when you think about it often, something positive comes out when you have these difficult conversations.
Real leaders can first initiate these types of discussions and structure them to make them worthwhile having.
Understand your strengths and weaknesses
Having self-awareness is an excellent strength for Assistants to have in general, but for leaders being aware of their strengths and weakness is essential.
If you can, complete a survey like Insights Discovery or Myers Briggs to see where your strengths and weaknesses lie as a leader and then you will have a good understanding of the areas that you can work on.