I've decided to + (verb)

I've' is short for 'I have' and including the word 'decided' you are stating that you have made a decision or come to a conclusion.

Here are some examples:

"I've decided to accept the job."
"I've decided to complete my degree."
"I've decided to change my bad habits."
"I've decided to extend my membership at the gym."
"I've decided to form a chess club."
"I've decided to hand over my responsibilities."
"I've decided to help you move."
"I've decided to interview for the job."
"I've decided to increase my work load."
"I've decided to manage a store."