Merging a Select query into a view
Just keep adding to your list of LEFT JOINs, like this:

Select 
  Atr.Ssn_Tx
 ,Names.First_Na
 ,Names.Middle_Na
 ,Names.Last_Na
 ,Reff.Ref_Cd_Desc_Tx Suffix_Na
 ,MBR.PRSN_MBRSH_ID
 ,(CASE WHEN Tax.FILLING_STATUS_CD IN (2061,2062,2063) OR  (Tax.FILLING_STATUS_CD=2063 AND Tax.PRIM_TX_FILER_IN ='Y') THEN 'PRIMARY'
             WHEN Tax.FILLING_STATUS_CD=2063 AND Tax.PRIM_TX_FILER_IN ='N' THEN 'SPOUSE'
             WHEN Tax.FILLING_STATUS_CD IN (2066, 2068) THEN 'DEPENDENT'
             ELSE 'Not sent to FDSH'
             END) AS FILTER_TYPE_CD
 From Hix.T_Enrt En Inner Join Hix.T_Prsn_Enrt Pe On En.Enrt_Id = Pe.Enrt_Id And En.Enrt_Status_Cd In (428,439, 430 ) And Pe.Active_In = 'Y' And (Pe.Retro_In Is Null Or Pe.Retro_In = 'N') 
Left Outer Join Hix.T_Aptc Ap On En.Enrt_Id = Ap.Enrt_Id
Left Outer Join Hix.T_Prsn_Addl_Attr Atr On Pe.Prsn_Mbrsh_Id = Atr.Prsn_Mbrsh_Id 
Left Outer Join
    (
                    Select nAc.Prsn_mbrsh_Id,  First_Na , Middle_Na , Last_Na, Suffix_Cd From Hix.T_Prsn_Name Na, Hix.t_prsn_mbrsh_prsn_name_ac nAc
                                                   where na.prsn_name_id = nAc.prsn_Name_Id
    ) Names On Pe.prsn_mbrsh_id = Names.prsn_mbrsh_id
Left Outer Join Hix.T_Ref_Data Reff On Names.Suffix_Cd = Reff.Ref_Data_Id
Left Outer Join Hix.T_Ref_Data Re On Atr.GENDER_CD = Reff.Ref_Data_Id
Left Outer Join Hix.T_PRSN_MBRSH MBR on MBR.PRSN_MBRSH_ID =  Pe.PRSN_MBRSH_ID 
LEFT OUTER JOIN HIX.T_PRSN_MBRSH_TAX Tax ON Tax.PRSN_MBRSH_ID = Pe.PRSN_MBRSH_ID AND tax.TAX_FL_YR_NB=YEAR(CURRENT DATE)-2


Assumption: your HIX.T_PRSN_MBRSH_TAX table has a PRSN_MBRSH_ID column (most likely this is the case)