Get some REMA patches in the 16mm size.
You can lay the patch on the tube and trace around it with a pen to show the area that has to have glue applied.

In general, removing the "dead" (oxidized) rubber is the key.
REMA kits include a piece of sandpaper which works well.
The cheap kits with the little metal scraper are a PITA. They are akin to applying bricks vs REMA.

IF your hole is well centered on the patch, you should be OK, assuming an otherwise good patch job.