Login to Admin Console and,

Enable following two under Weblogic domain > Advanced options

Platform MBean Server Enabled

– Specifies whether each server instance initializes the JDK’s platform MBean server
– This makes it possible to access the WebLogic Server MBeans and the JVM platform MXBeans from a single MBean server.
– Local processes in the JVM can directly access this MBean server

Platform MBean Server Used

–  Specifies whether WebLogic Server will use the platform MBean server for its Runtime MBean Server
–  Default value is “true” over wls 10.3.3.0 inclusive

Add this in server start via Admin console and restart server(s)

-Dcom.sun.management.jmxremote.port=6001
-Dcom.sun.management.jmxremote.ssl=false 
-Dcom.sun.management.jmxremote.authenticate=false 
-Djavax.management.builder.initial=weblogic.management.jmx.mbeanserver.WLSMBeanServerBuilder

OR add following in start-up scripts and restart server(s)

JAVA_OPTIONS="-Dcom.sun.management.jmxremote.port=6001"
JAVA_OPTIONS="${JAVA_OPTIONS} -Dcom.sun.management.jmxremote.authenticate=false"
JAVA_OPTIONS="${JAVA_OPTIONS} -Dcom.sun.management.jmxremote.ssl=false"
JAVA_OPTIONS="${JAVA_OPTIONS} -Djavax.management.builder.initial=weblogic.management.jmx.mbeanserver.WLSMBeanServerBuilder"
export JAVA_OPTIONS

Use JCONSOLE And/Or VisualVM for monitoring CPU/MEM, All kinds of Mbeans etc.

How to monitor applications and much more,

Jconsole in Jdk7

Jconsole in Jdk8

VisualVM Jdk8