Hopefully you bought a replacement battery with Solder tabs. I found mine on eBay.

The solder tabs on your replacement battery may not line up with where you need them, mine didn't.

I soldered one tab in place directly, then soldered some stranded wire to bridge between the second tab and the circuit board. I trimmed and bent the second tab a little to make this work. It was easy to solder the wire to.

Read the comments...some people smarter than me have soldered in battery holders to make changing the battery easier in the future. Genius!