Older QGIS 2.4 version installation in Ubuntu 14.04 instead of QGIS 2.8

Right now I am trying to run SWMM model on QGIS2.8. But the swim plugin is not compatible with 2.8 version of QGIS. Can anyone suggest me how to download and install qgis 2.4 on Ubuntu 14.04.

It would be great to give me a detailed answer rather than referring the answer to other websites. Because i have tried everything available on google. But nothing is working to me.

I tried downloading tar gz file of qgis 2.4 from the official website. The preinstallation process of configuring and making file is not working.

Any answers are welcomed.

Thank you in advance