You must first deposit your preprint on a preprint server, such as bioRxiv or arXiv, to obtain a DOI.
Your preprint must not be published or under consideration for publication elsewhere at the time of its submission to PCI Ecology. If your preprint is sent out for review by PCI Ecology, you are not permitted to submit it to a journal until the PCI Ecology evaluation process has been completed. You cannot, therefore, submit your preprint to a journal before its rejection or recommendation by PCI Ecology.
You must be aware about the timing of the process. It can take up to:
20 days before a recommender decides to handle your preprint and therefore to send it out for peer-review.
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