How do you close out a "writing a put" position before expiration date?

I sold a put for $1 (100 shares) for $100 premium with an expiration date of October 19. The put is now worth 0.45, so I've made $55 at this point.

How do I close out the position for a $55 gain right now instead of waiting for expiration? The reason I want to is because I have collateral tied up that I want to use.

Submitted October 12, 2018 at 11:32PM by JumpingGhost21 https://ift.tt/2CHUj5O