Populate/merge/connect New WP Site (MySQL database) with Post from Old Site

How do I populate/merge/combine my old WP Site (MySQL database) with Post from New Site? If Connect/include are better words than populate or merge…But, the idea is to pull posts in archive on the topic in search… The databases are the same, the materials and contents are the same etc. Are there scripts that could be uses? …Plus I’m working within the phpMyadmin platform? Any help is greatly appreciated!