How to cite uproot and awkward arrays (by Jim Pivarski)?
You can cite the paper using the arxiv number and add a link to the github repo in a footnote. As a basic example:

Methodology
In this work, we make use of the uproot package* for array
calculations [1].
* www.github.com/scikit-hep/uproot
Bibliography
[1] Pivarski et al., &quot;Awkward Arrays in Python, C++, and Numba&quot;,
arxiv: 2001.06307