Working memory (WM) serves as an interface between perception and long-term memory (LTM), yet how active processing within WM shapes pre-existing LTM representations remains incompletely understood. Across two behavioral and electroencephalography (EEG) experiments, we examined how attentional prioritization (via retro-cuing) and retrieval testing in WM affect the subsequent precision and neural reinstatement of previously learned object-location associations in LTM. Participants first learned object-location associations in an initial LTM encoding phase, then encountered a subset of these objects in a WM phase involving retro-cues and delayed testing, and finally completed a continuous spatial LTM retrieval test. Both attentional selection in WM and WM testing improved subsequent LTM location recall precision. Event-related potential (ERP) and multivariate decoding analyses revealed that processing items in WM enhanced neural signatures of LTM retrieval and strengthened cross-phase representational similarity. Together, these findings demonstrate that active processing in working memory boosts existing long-term memory representations and facilitates their subsequent retrieval.