1) perform all the necessary pre-upgrade maintenance steps
2) stop aem 6.2
3) unpack the 6.5 jar OVERTOP the existing crx-quickstart
java -Xmx4096m -jar aem-quickstart.jar -unpack
4) perform the mandatory repository migration to upgrade the segmentstore to oak-segment-tar. You need to get this right -- there are various profiles that are applicable depending on how your 6.2 is set up. So understand the different profiles and apply the correct one.
For example if everything is in the segmentstore tar files, and there is no datastore you would use :