Once you have logged into the H5P website find the Create New Content button (it is usually on the Content tab of your account).
Add the name of your content to the Title field and then choose Audio Recorder from the Select content type dropdown menu by clicking on the appropriate Use button.
Add your instructions to the Task Description field. Clicking on the down arrow next to Localization: Record will reveal a lot of settings such as button titles and download options. Leaving the default settings as they are seems to work fine but feel free to experiment with different options if you want to.
Add any tags to the Tags section and choose whether you want to display the buttons listed below with your audio recorder. Personally I would leave all of the buttons checked as per the default settings as it gives both you and your users more flexibility. Then click on the Save button.
If you click on the Embed button at the bottom of the audio recorder once it has been generated, you can copy the HTML code and embed it into a web page just like this: