How to cite my own submitted but not yet published work?
In principle you can cite other, submitted work in a research paper. Just give the authors, paper title, and either "Submitted." or "Submitted to [venue]." in the reference list.

However, both as a reviewer and reader, I usually find this disappointing. I already came across several cases where I wasn't able to find the cited paper even years after publication of the paper with the citation. It is well possible that the cited paper is rejected, and maybe someone just doesn't follow up to really get it published. As a better alternative, check whether you can put a preprint version of the paper you want to cite online (e.g. on arxiv), and just cite that.