I fucked up (router)

so Im an idiot and decided to install custom firmware, I have never done this before

so I went int omy tp link router defualt gateway

found the way to update firmware and tried to install dd-wrt

but someth8ing went wrong and now whe nI have it connect to my pc with an ethernet cable and I disable all other access to the internet, when I put ipconfig in the command promt it has no defualt gateway

how to I connect to it again so that I can install the right firmware, and how do I do that?

thanks in advance