Leading from the side means engaging in a more democratic process whereby each decision is discussed with other team members and the person leading the group has no more power than any other person on the team to determine the direction.
However, if you are leading from the side it means you aren't officially in charge but can still significantly impact the group dynamic in a few ways:
1. You can support the president in their efforts
2. You can explain what's happening to team members who may be confused
3. You can initiate projects and ideas for the group to consider
4. You can contribute to finding solutions
Basically leading from the side means exerting influence to get things done. It doesn't mean you have an ulterior motive, but rather that you understand the purpose of the group is to get things done and move forward. It could be that personalities on your team are resistant to some of what the president or others have suggested. Leading from the side puts you in a position to change those perceptions and help move the group along without actually being the leader.
Have you ever tried to lead from the side?