The upgrade process is same regardless which version of DNN your are upgrading.

1)      Make backup of all DNN files and obtain a full backup of DNN database. This is critical in case something goes wrong, never skip this step.

2)      Upload/overwrite exsting DNN files with the new DNN version.

3)      Open new web.config file and copy paste the connection strings and machine validation key from the original web.config that you have in your backup.

4)      If you are religious, pray a bit. Then browse to your domain, if auto upgrade is enabled in the web.config (by default it is on) you should see DNN upgrade log show you the upgrade process.

If everything works well, you should have a working DNN site.

NOTE: If you are upgrading from 4.8.2 to 4.8.3 you can skip step 3 .. refer to Charles' blog posts about the XML Merge function added in ( I believe ) 4.6.X. 

So, just unzip 4.8.3 UPGRADE package over your existing 4.8.2 web site, then browse to your home page. the upgrade will auto-kickoff and automatically manage migrating your old web.config to the new one. You never need to open or look at a config file again :)