Check original Play! Framework migration documentation first:
a) change Play! version from
<properties>
...
<play2.version>2.5.14</play2.version>
</properties>
to
<properties>
...
<play2.version>2.6.0-M4</play2.version>
</properties>
b) add dependency
<dependency>
<groupId>com.typesafe.play</groupId>
<artifactId>play-guice_2.12</artifactId>
<version>${play2.version}</version>
</dependency>
c) if using Java forms add dependency (previously it was part of Play! Java module)
<dependency>
<groupId>com.typesafe.play</groupId>
<artifactId>play-java-forms_2.12</artifactId>
<version>${play2.version}</version>
</dependency>
and optionally configure additional template imports
<plugin>
<groupId>com.google.code.play2-maven-plugin</groupId>
<artifactId>play2-maven-plugin</artifactId>
<version>${play2.plugin.version}</version>
<extensions>true</extensions>
<configuration>
...
<templateAdditionalImports>play.data._ play.core.j.PlayFormsMagicForJava._</templateAdditionalImports>
</configuration>
</plugin>
d) if using Java JPA upgrade Hibernate version to 5.x (e.g. 5.2.6.Final)
e) if using Ebean upgrade play2-ebean dependency version to 4.0.0-M2
This will require some changes in model classes, e.g.: