Online submission can be done through the editorial manager on the ScholarOne website.

Instructions for authors can be found this page, which includes a link to a LaTeX style template available on Overleaf. 

Regarding Electronic Supplementary Information (Data sets and computer code)

In the interest of transparency and reproducibility of results, Psychometrika strongly encourages authors to include with published papers, where possible, electronic supplementary materials to be published online in an open-access repository (e.g., the Open Science Framework, or a repository listed here). Online supplementary materials can include data and statistical-software code. Data and code should be clearly documented to allow replication and verification of the results presented in the final version of the paper. Authors should cite their supplementary material in the paper they submit for peer review, so it can be taken into account during the review process.