Since song is already created,and the melody feels really instrumental
but would like to add some lyrics.

Any tips or different techniques if i create lyrics to fit the song,instead of doing lyrics first then the melody?
hum out what kind of melody you want the song to follow... because the melody you sing probably won't be anything like the guitar part.

go through it a few times... then when you've got the melody engraved into your mind, start changing the humming into lyrics... get something down to start with, it will probably sound crap but build on it... and hopefully after a while you'll have something you're happy with.

worst comes to worst... chuck a blinding 4minute guitar solo in there instead of the lyrics =]

well its actually my friend who made a piano song and soon the rest of us baugh a durm, guitar and started getting a whole typical"band song" happening. but we have no lyrics.

The song is quite repetitive though to my taste, but very ingaving to your head lol.