First copy your jar file and paste into you Android project's libs folder.
Now right click on newly added (Pasted) jar file and select option
Build Path -> Add to build path
Now you added jar file will get displayed under Referenced Libraries. Again right click on it and select option
Build Path -> Configure Build path
A new window will get appeared. Select Java Build Path from left menu panel and then select Order and export Enable check on added jar file.
Now run your project.
More details @ Add-JARs-to-Project-Build-Paths-in-Eclipse-(Java)