These are the steps you need to follow:
1. Launch eclipse and then go to help, then click install new software.
2. In the Repository dialog box, give name as "Force.com IDE" and the location.
3. After that, click ok.
4. Now, it will going to download the list of available plugins.
5. After that you need to check the box which is next to Force.com IDE and then click next.
6. After that, Eclipse download and install it.
7. Once done, restart eclipse.
8. After that, select window and then go to Open Perspective, choose other, then select Force.com and then click OK.
I hope this will help.
Want to become a Salesforce expert? Then, you should join our salesforce lightning training today!
Want to know more about Salesforce? Watch this video on Salesforce Training | Salesforce Administrator training: