If you received Notice of Allowance (NOA) from the USPTO that means you are close to registering your trademark. The USPTO has decided your trademark is allowed and you now have to demonstrate to them that you are currently using your trademark in commerce. A Statement of Use (SOU) is what will demonstrate that you are doing so. You have 6 months from the NOA to file an SOU or an Extension. An Extension will grant you an additional 6 months to file an SOU. Up to six Extension may be filed for a total of all 3 years, although note that all applicable fees must be paid for each Extension. To file an SOU you will need to pay the fees and submit a specimen that shows that you are using your trademark in commerce. The SOU must recite that you are using your trademark in commerce, the date you first used your trademark, and on what goods/services from the NOA you are using you trademark on. You must be using your trademark on all goods/services contained in the NOA at the time you file the SOU. If you are not, then those items must be disclaimed (removed) from the application. Failure to do so could jeopardize your mark. Attention to detail is very important which is why it is recommended to have a licensed attorney prepare such filings.
This blog is not legal advice and is not specific to your application. You should always consult an attorney.