Do I have to activate a new ram?

I have built in my laptop a 8gb gddr4 ram module.

The additional ram is displayed but you can see no difference and taskmanager will also use at most the normal 8gb gddr4.

What do you have to do?

Windows occupies just as much RAM as the current programs just need. If the applications you use do not need more ram then you will not be able to take any more, no matter how much you install. With more ram, your PC will not get any faster, it will only get very slow and sluggish if you have too little.

If you want to fully utilize your ram you have to make many applications at the same time then your pc also uses the full 8gb