Start with downloading the eclipse package from here NetSuite recommends Eclipse IDE for Java EE Developers.
Unpack the archive file you downloaded, and place it in the root directory on your hard drive.
Now update Eclipse with SuiteCloud IDE package from the SuiteCloud IDE update site.
Add the SuiteCloud IDE Update Site:
1.Launch Eclipse. If you are prompted to select a workspace, accept the default.
2.Go to Windows > Preferences. The Preferences window appears.
Add the SuiteCloud IDE update site as follows:
In the navigator, select Install/Update & Available Software Sites.
Click Add. Pop up will come then enter below detais
Name as SuiteCloud IDE Update Site
Location as click here!
SuiteCloud IDE Update Site appears in the list of Available Update Sites. Leave all other sites checked.
To install SuiteCloud IDE:
Go to Help & Install New Software. The Install window appears.
In the Work with dropdown list, select SuiteCloud IDE Update Site.
In the Name column, select SuiteCloud IDE.
Click Next to view the installation details.
Accept the terms of the license agreement and click Finish.
Eclipse installs SuiteCloud IDE. When the installation is complete, click Yes to restart Eclipse.
When Eclipse restarts, the SuiteCloud IDE Setup Wizard opens.
You can verify the Installation by doing below steps
Go to Help & About Eclipse.
Click the NetSuite icon or click Installation Details to open the About Eclipse Features window.