Throw your hat into the ring
Definition 1 of 1
Pro Tip 1/3Metaphorical Origin
Originally refers to literally throwing a hat in a boxing ring to challenge someone, now a metaphor for entering any competition. 
She finally decided to throw her hat into the ring for the position of head editor.
Pro Tip 2/3Initiative Shown
Using this phrase often shows a person's readiness and determination to take on a challenge voluntarily. 
After years of training, he's thrown his hat into the ring for the marathon.
Pro Tip 3/3Informal Context
The phrase is informal, more suitable for casual conversation than formal announcements or writings. 
In our meeting, Jenna threw her hat into the ring to organize the company retreat.