how to amplify current coming out of n channel mosfet
You don't need to "amplify the current". It will flow automagically when you switch the LEDs on. The thing is that you need a switch (MOSFET or BJT) which can stand the 2A.
A power MOSFET would be ideal, since they're available with very low \$R_{DS}(on)\$, so they won't get very hot. You can do a parametric search on this Fairchild page. For example the FDN339AN and FDN359BN have low \$R_{DS}(on)\$.
An other option is to use a darlington transistor. They're not ideal though: \$V_{CEsat}\$ is rather high, often 2V, so when you run 2A through them you need some cooling.