To submit a preprint, you must first deposit it on a preprint server, such as bioRxiv or arXiv, to obtain a DOI.
Your preprint must not be published or under consideration for evaluation elsewhere at the time of its submission to %(longname)s. If your preprint is sent out for review by %(longname)s, you are not permitted to submit it to a journal until the %(longname)s evaluation process has been completed. You cannot, therefore, submit your preprint to a journal before its rejection or recommendation by %(longname)s.
You must be aware about the timing of the process. It takes:
up to 20 days before a recommender decides to handle your preprint and therefore to send it out for peer-review.
a mean time of 50 days before a recommender takes a decision based on the first round of peer-review
The evaluation of your preprint might take several rounds of review before the recommender take the final decision to reject or recommend your preprint.
Details about the evaluation & recommendation process can be found here
To submit a preregistration, please follow the instructions found here.