sql, how to change the data type after data loading?

hi Experts,

I have loaded an excel file in the database by using sql import wizard. It automatically generated a table, like below.

CREATE TABLE [dbo].[tblCSOMonthlyLCDetail](
	[ContractString] [nvarchar](255) NULL,
	[LoanStoreID] [float] NULL,
	[CustomerFirstName] [nvarchar](255) NULL,
	[CustomerLastName] [nvarchar](255) NULL,
	[LoanDate] [datetime] NULL,
	[OPB] [money] NULL,
	[Score] [float] NULL,
	[CSOFees] [money] NULL,
	[LienFees] [money] NULL,
	[LateFees] [money] NULL,
	[Renews] [float] NULL,
	[Dayslate] [float] NULL,
	[MarkerID] [float] NULL,
	[FileDate] [datetime] NULL
) ON [PRIMARY]

GO

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After I loaded all data in this table, and I want to change data type for a few fields, the expected table structure will be like below.

CREATE TABLE [dbo].[tblCSOMonthlyLCDetail](
	[ContractString] [nvarchar](255) NOT NULL,
	[LoanStoreID] [int] NULL,
	[CustomerFirstName] [nvarchar](255) NULL,
	[CustomerLastName] [nvarchar](255) NULL,
	[LoanDate] [datetime] NULL,
	[OPB] [money] NULL,
	[Score] [int] NULL,
	[CSOFees] [money] NULL,
	[LienFees] [money] NULL,
	[LateFees] [money] NULL,
	[Renews] [bit] NULL,
	[Dayslate] [int] NULL,
	[MarkerID] [int] NULL,
	[FileDate] [datetime] NULL
) ON [PRIMARY]

GO

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Can you help me on it?  Thanks.