1-If you obtained Na free MEL , then Na could be incorporated by ion exchange process.

2-Other route is to use the basic solution of NaOH in the batch of synthesis.

3-The question is have you obtained  pure MEL ?  Or you ask how obtain MEL ? which template did you use in case you obatined it?

I suppose that you already have a pure H-form MEL zeolite, if so, a simple ion exchanged of the zeolite by NaNO3 solution for a couple of cycles, followed by   calcination will do.

First, you need to get the pure MEL, and then you can mix it with the NaOH solution. The next for your sample is the calcination.

Mixing with NaOH could change the zeolite structure (especially Si/Al ratio). I recommend you ion-exchange with NaNO3 solution couple times. 

I agree strongly with Evgeny NaOH  will change the Si/Al zeolite ratio. Use of NaNO3

highly recommended at about 0.1M -higher concentrations could allow salt imbibition..Exchanged  zeolite should be washed wth deinonised water.