Hi there, and welcome, then!
It's actually fairly easy. Once you've logged in the main site, go to the album you want to review. Click on the little wrench icon that can be found either at the top of the page, below the band name:
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or also near the album title when in the band page:
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and then select 'Write a review' in both cases.
What you will find is pretty self-explanatory. At the bottom of the text field you'll have the 'Submit to queue' button (roughly where 'Publish' is in the picture below):
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Once you send the review to the queue, the mods will evaluate it and either accept or reject it (in the latter case, explaining the possible issues). During this lapse of time you won't be able to edit it, so make sure it follows the rules written at the top of the review page.
That's pretty much it! Have fun
