To configure the logging for WildFly, edit the $WILDFLY_HOME/standalone/configuration/standalone.xml file.

To customize the logging properties, find the <profile> node and then find <subsystem xmlns='urn:jboss:domain:logging:3.0'> inside it.

It is based on handles like this:

<console-handler name="CONSOLE">
                <level name="INFO"/>
                <formatter>
                    <named-formatter name="COLOR-PATTERN"/>
                </formatter>
            </console-handler>
            <periodic-rotating-file-handler name="FILE" 
             autoflush="true">
                <formatter>
                    <named-formatter name="PATTERN"/>
                </formatter>
                <file relative-to="jboss.server.log.dir" 
                 path="server.log"/>
                <suffix value=".yyyy-MM-dd"/>
                <append value="true"/>
            </periodic-rotating-file-handler>
            <logger category="com.arjuna">
                <level name="WARN"/>
            </logger>
            <logger category="org.jboss.as.config">
                <level name="DEBUG"/>
            </logger>
            <logger category="sun.rmi">
                <level name="WARN"/>
            </logger>
            <root-logger>
                <level name="INFO"/>
                <handlers>
                    <handler name="CONSOLE"/>
                    <handler name="FILE"/>
                </handlers>
            </root-logger>
            <formatter name="PATTERN">
                <pattern-formatter pattern=
                "%d{yyyy-MM-dd HH:mm:ss,SSS} %-5p [%c] (%t) %s%e%n"/>
            </formatter>
            <formatter name="COLOR-PATTERN">
                <pattern-formatter pattern="%K{level}%d
                {HH:mm:ss,SSS} %-5p [%c] (%t) %s%e%n"/>
            </formatter>

By default, it will rotate daily:

            <periodic-rotating-file-handler name="FILE" 
             autoflush="true">
                <formatter>
                    <named-formatter name="PATTERN"/>
                </formatter>
                <file relative-to="jboss.server.log.dir" 
                 path="server.log"/>
                <suffix value=".yyyy-MM-dd"/>
                <append value="true"/>
            </periodic-rotating-file-handler>

If you want it to rotate based on the size, you should remove the preceding handler and then insert this one:

            <size-rotating-file-handler name="FILE" autoflush="true">
                <formatter>
                    <pattern-formatter pattern="%d{yyyy-MM-dd 
                     HH:mm:ss,SSS} %-5p [%c] (%t) %s%e%n"/>
                </formatter>
                <file relative-to="jboss.server.log.dir" 
                path="server.log"/>
                <rotate-size value="2m"/>
                <max-backup-index value="5"/>
                <append value="true"/>
            </size-rotating-file-handler>

In this case, the log will rotate when the file reaches 2 MB and will keep a history of five files in the backup.