Create a path to the SharePoint command line tools

The following steps make it easy to run common SharePoint administrative tools such as STSADM and PSCONFIG from a command line without having to navigate to folder that contains these tools.
1. Select Start > Control Panel > System
2. Under the Advanced tab select ‘Environment Variables’
3. Select the ‘Path’ variable, click ‘Edit’ and enter the following text (note the semi-colon):
;C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\12\BIN
4. Close any open command windows to allow the change to take effect

Steps To Install WSP file in STSADM

1. Add the solution
stsadm -o addsolution -filename {WSPFILENAME}
2. Deploy the solution
stsadm -o deploysolution -name {WSPFILENAME} -url {SITEURL}
3. Install the feature
stsadm -o installfeature -filename {FeatureFolder}\feature.xml
4. Activate the feature
stsadm -o activatefeature -id {FEATUREID} -url {SITEURL} -force
5. Deactive the feature
Stsadm.exe -o deactivatefeature -filename “C:\Program Files\Common Files\Microsoft Shared\web server extensions\12\TEMPLATE\FEATURES\ViewFormPagesLockDown\feature.xml” -ur http://servername/
6.Uninstall the feature
stsadm -o uninstallfeature -filename
7.Retract Solution
stsadm -o retractsolution

-name

[-url]

[-allcontenturls]

[-time]

[-immediate]
8.Delete Solution
stsadm -o deletesolution

-name

Reference