James:
First, adjust the DPI setting of your scans, and make sure you crop your scans to include only the stamp/area you wish to post.
Most photos & images you see on the web are 72 dpi. But sometimes when you're trying to show detail of a stamp, that's a little low. On the other extreme, modern scanners that default to 1200 dpi are just too hi-res. You'll never get the filesize under a megabyte.
There's a tutorial on the left about uploading photos. Also, try the search function to find other threads and discussions.
A few of the members here prefer to post their scans on a different picture sharing site and post links to the larger off-site images. In my opinion, this is less desirable because sometimes the images disappear over time and ruin older threads for new members. However, I confess that on occasion, I too have used off-site image storage.
Here's a tutorial I did a while back ....
https://goscf.com/t/11977Finally, I'll say that it took every SCF member a week or two to figure out the best way to post images -- don't get discouraged; you'll get the hang of it soon.
KirkS