Another Computer Connection At Home.?

Hi.I have a DSL from att at home for one computer. not wireless. only this tiny modem with 1 connection for my PC that connects to my phone line with a splitter/filter that separates the connection for the phone line and PC.
My wife bought a mini notebook, ACER, the one they sell at att wireless. we got the data plan for it but cant get a good signal in our house. bad reception. Anyway, is there a way that I can have another internet connection for the mini without asking for another modem from att? or any way to get a better signal? I’m not very tech savVy, so idiot proof words would be appreciated (lol).
OR, am I stuck with what I have, have to spend more for another modem, or throw that damn mini!
Please let me know what my best options are/is.