You can attach a jar in Eclipse by right-clicking on the Project → Build Path → Configure Build Path. Following the Libraries tab, click Add Jars or Add External JARs and deliver the Jar. A fast demo here.
The above resolution is a "Quick" one. Still, if you are operating on a project where you require to allocate files to the origin control container, I would recommend attaching Jar files to a dedicated library folder inside your source control container and referencing a few or all of them as stated above.