Unable to flash hAP lite RB941-2nD-TC

[Willy]

It was there...Here we go again:

How can I change my router's lan port to wan port?

I'm using TP link TL-WR840N v2 router. Somedays ago during storm my router's wan port got damaged and it's not working. My other lan ports are okay. I want to make one of lan ports to wan port. How can I do that? I installed OpenWrt in my router by firmware upgrading last night. I'm still novice/new in OpenWrt. So your kind helping will be much appreciable.