Where to Find and Catch Helioptile
From Pokemon Go Wiki
Helioptile are found and captured in Nest and Habitat locations.
Nests
Helioptile Nests are locations that consistently spawn Helioptile.
Habitats
Helioptile Habitats are spawn locations where Helioptile is likely to be encountered, but not guaranteed the way a Nest is.
Additional Tips and Information
Best Nests
If you know a really good nest or any of the nests above is really good, list them here: