Hi,
I assume you have an all-in-one Maven project. Then you can add external AMPs that are available in an external maven repository as follows:
For Alfresco.war (repo extensions), use the following POM:
all-in-one/repo/pom.xml
So you would add a dependency for your external AMP and then add it also as an overlay for the maven-war-plugin. See commented out example for alfresco-spp AMP.
Same thing for Share.war extensions, use the following POM:
all-in-one/share/pom.xml