If you have more than a couple of pictures you want to attach to your logs, you might Upload pictures in bulk.
In order to write the individual logs, you find the first log you are gonna write, and click on the link in the list:
You then get a page with a lot of information on it:
You write your log in the text-field (1). As with the template, you may write in Markdown, and use the help under the field. In order to help you remember more of the place, you find a Streetview of the cache if that is available (2), a map of the place (3) and you may have the terrain displayed by the leaflet you prefer in (4). If you have field notes from the cache, they are placed under the log (5) and uploaded pictures are displayed in (6). To upload an image to this specific log, you find this possibility in the menu on top of the logging-window. Have you and your friends allowed third-party-developmenters to see the geocaching activity, you find logs from your friends at (7). Aditional Travel Bugs may be added at ( 8 ) and you may preview your log with the template with (9).
Be sure to save your logs either by save and go to next or just save (10).
You may always go back and edit your template before publishing it to the cache-page. That is why there are a good reason to use the trip specific template. You are less likely to do an edit that affects the wrong caches.