Also, the format for timestamps should be:
hours:minutes:seconds,milliseconds
Note the comma!
So really your file should look like:
1
0:00:00,000 --> 0:00:01,590
Welcome to my video
2
0:00:02,000 --> 0:00:09,590
I'm going to show you how to change a lightbulb
Also make sure to put two blank lines at the end of the file, or else it doesn't seem to load the last subtitle. I don't think this bit is a requirement of the SRT standard and is probably just a VideoPad quirk. I should check if this is a bug or not.