Computer internet problems?

[Amber]

I have a Lenovo computer and it came with a lot of programs that I wanted to erase I started erasing a lot of programs but I realized I wasn't connected to the internet anymore I have no idea what i did and how I can fix it, the internet is not broken because my sister can access it on her computer it's just not working on mine everytime I connect it the cables username doesn't even show up either please help me