How to Increase videoram

[TheOriginal]

When i go to control panel...i see that i have a nvidia GTX750 ti
it says i CAN have 4G
but it only uses 2G

how can i increase this?

picture: http://imgur.com/NKe4tHn
(sorry this is in dutch)

 

[TechyInAZ]

What exact model is your GTX 750 ti?

 

[TheOriginal]

What exact model is your GTX 750 ti?

how can i make sure?

 

[TechyInAZ]

What model is your GTX 750 ti? As in what manufacturer produced your gtx 750 ti?