Hi if anyone can help me please, I am baking a red velvet cake from a box (adams extract). I need to dense this up for the cake I am making. Its a three tiered cake for Saturday. If anyone has any suggestions please it would be greatly appreciated. TIA

Do you want to "dense it up" because you like that texture better or because you're stacking it?  If it's because you want to stack it you don't need to do that.  It's your support system that holds the cake, not the cake itself.  If you just want to make dense cake you can add a bit of flour to the mix.

Generally my rule of thumb is: an extra egg, 1 pkg of chocolate instant pudding (since it's a RV cake), and use buttermilk for your liquid.