I assume you mean blocking said hash using Threat Prevention blades.
If you mean something else, please elaboate.
To import one or more hashes, they must be placed in a file (CSV or STIX), then imported.
Refer to the following screenshot for where to do that:
Refer to the documentation for the correct format of this file: https://sc1.checkpoint.com/documents/R80.40/WebAdminGuides/EN/CP_R80.40_ThreatPrevention_AdminGuide/...
Note that in releases prior to R80.40, only MD5 hashes are supported.
R80.40 supports SHA-1 and SHA-256 hashes.