Following APA rules, both the title and subtitle of an article should be in sentence case, a style of capitalisation where only the initial word of a sentence and subtitle and proper nouns (e.g. places/ personal/ organisation names) receive capitalisation, while all other words remain lowercase. A colon (:) is employed to distinguish the title from its subtitle. Here's an example:

Ng Chok, H., Lewis, P., Mannix, J., Dickson, C., & Wilkes, L. (2021). Milestones in the journey: The story of refugees becoming registered nurses in Australia. Journal of Advanced Nursing, 77(11), 4525–4536. https://doi.org/10.1111/jan.14971