Check original Play! Framework migration documentation first.
a) change Play! version from
    <properties>
        ...
        <play2.version>2.1.5</play2.version>
    </properties>
to
    <properties>
        ...
        <play2.version>2.2.6</play2.version>
    </properties>
b) change groupId of all Play! dependencies from play
        <dependency>
            <groupId>play</groupId>
            <artifactId>play-xxxx_2.10</artifactId>
            <version>${play2.version}</version>
        </dependency>
to com.typesafe.play
        <dependency>
            <groupId>com.typesafe.play</groupId>
            <artifactId>play-xxxx_2.10</artifactId>
            <version>${play2.version}</version>
        </dependency>