The short answer is socialize constantly - it's an "always on" function for internal alignment and awareness. Ideally, any PMM KPIs will clearly map to both top-level company goals (revenue, net retention, product usage) and a shared understanding of "who does what"/"how a bill becomes a law" for your company's GTM motion. If your business is a fast-twitch, bottoms-up, Product Led Growth motion - it needs to be really clear what the PMM team is doing to drive triggers for acquisition, activation and maturity. In this case, the feedback will come in quickly as to what's working and what's not and thus the PMM team can use those KPIs to strategize with product and the rest of GTM.
For slow-twitch, traditional enterprise sales motions, PMM needs to have clear KPIs for the awareness and consideration phase (messaging informing campaigns that drive opportunity creation, first and third-party content that drive "see a demo," "talk to sales" and other hand-raising activity) as well as for the long haul of sales cycles that can take months or quarters. This is where you need to be plugged into the pipeline and how account teams can move opportunities to close with content, programs, campaigns and events. Designing ways to programmatically move opptys to close will not only socialize your KPIs but also make you a valuable partner to the rest of the GTM org who might have limited, out-dated views of what PMM does.