I've read some pretty lousy reads about deploying web parts and WSP packages to SharePoint. This is one of the best ones:
Long story short, here are the commands that get you 90% of what you need.
stsadm.exe -o addsolution -filename C:\WSSDistillery\Deploy\WSSDistillery.Deploy\WSSDistillery.Deploy.WebPart.wsp
stsadm.exe -o deploysolution -name WSSDistillery.Deploy.WebPart.wsp -url http://mossserver:28921 -immediate -force
stsadm.exe -o execadmsvcjobs
stsadm.exe -o installfeature -filename WSSDistillery.Deploy.WebPart\Feature.xml -force
stsadm.exe -o activatefeature -filename WSSDistillery.Deploy.WebPart\Feature.xml -url http://mossserver:28921 –force
Jason Apergis, the author of this post, has written probably the single best article about Deploying to SharePoint, and you're doing yourself a disservice by not clicking on that link.