Easy? Depends.
If there are no cells preset to accept strings only (under Format Cells...>Numbers>Format code>@
) and containing something starting with the character =
(correction thanks to JohnSun: or the pair of characters {=
} , you find cells containing a formula with the help of >Edit>Find & Replace
.
Enable Regular expressions
.
Enter ^=
behind Find:
Correction: Edit ^\{?=
behind Find:
Select Formulae
behind Search in:
Click Find All
All the cells containing formulae are now selected, but the mode of selection is non-standard. Therefore you need to:
Ctrl+Click on one of the found cells twice.
Rightclick on that cell now to open the context menu.
Select the menu item Format Cells...
and make the settings you want.
See this example. So easy!
If there are texts … containing =
as the first character … : Edit your question and append this specific requirement.