There are a few ways to insert a check mark in Excel. The easiest way is to use the Wingdings font.

To insert a check mark using Wingdings, type "222" and press "Enter".

You can also use the Symbol font. To insert a check mark using Symbol, type "☑" and press "Enter".

Finally, you can use the ASCII code for a check mark. To insert a check mark using ASCII, type "27" and press "Enter".