On Profwriting.com it is free to sign up as a Writer.
As a Writer you can review other people's uploaded manuscripts – in fact we encourage you to do so. Here's how:

1. First you need to make an account as a Writer.
2. Then login with the details emailed to you.You are now ready to review.
3. To review, click on the link to find a Writer's Manuscript from the Peer Reviews menu. You are then presented with a simple form on which you can write a review and give a five-star rating.

Please watch the video below for a visual guide.

Submission form guidelines.

Review: Enter your review; remember to be honest but constructive with your comments.
Star Rating: One star is low, five stars is high. The ratings get averaged as more reviews are added.