Adding group to the particular list or library in sharepoint

Hey Madhusudana_Yadav_N ,

You mean you have a a list/library with a fied of type "User/ Group" and you want to set this value from your SPFX solution?

If yes, then you can use the PnPJS library to update it. Considering you have a field "Owner" of type User/ Group and a "Members" field that supports multiple Users/ Groups, you can update it using:

sp.web.lists.getByTitle(<ListTitle>).items.getById(<ItemID>).update({
     OwnerId: <UserId>,
     MembersId: {
          results: [<User1ID>, <Group1Id>]
     }
})

 So basically, you need to append "Id" to the end of the field name and set it to ID of the User/ Group you want. If it is a multiple people field, then you have to set it to an object containing a "results" array, in which each value is an user/ group ID.

Hope it helps.