It's still about 20% of psych residency spots that go to IMGs (down from 40% at one point), and many IMGs are still ranked more highly than US students who go unmatched. It is important to have high board scores as possible, get ECFMG certified, complete step 3 (for those needing an H1 visa, not relevant for the OP), get 8 weeks worth of psych electives at institutions with psych residency programs in the US while still a medical student (observerships and externships upon graduation carry much less weight), obtain 2-3 strong LoRs from said electives, and demonstrate a strong commitment to a career in psychiatry. IMGs wanting to match at academic programs and have an academic career will need to have significant number of publications (ideally first author in high impact factor journals), presentations at national and international meetings, and consider a postdoc at an institution of interest (this is one of the only ways of getting into the most competitive programs for IMGs - work with an influential PI who will get you into that residency program).