"finalize your decision" is correct and usable in written English. You can use it when you want to emphasize that a decision should be completed and put into practice. For example, "We need to finalize our decision on the new website design by the end of the week.".
Finalize your decision.
This will finalize your decision.
Finalize your decision is both a milestone for you and your riding career.
Finalize your decision for the placement and arrangement of your newly added field.
Review the contract fully before finalizing your decision.
Before finalizing your decision on the company that will install the solar panels for your home, make sure to ask them of what will happen in case you encounter problems with the equipment after it has been installed.
Finalize your keyword or key phrase decision.
Being a terminologist, I care about word choice. Ludwig simply helps me pick the best words for any translation. Five stars!
Maria Pia Montoro
Terminologist and Q/A Analyst @ Translation Centre for the Bodies of the European Union