You need to explicitly write every column you need to handle in your insert, excluding those having some autoincrement, default, ...
This is however a good idea, even if you don't need it, because it gives you more control and a more readable code:
insert into xxacl_pn_project_link_h(
                                    HISTSEQ_NO         ,
                                    HIST_DATE          ,
                                    MKEY               ,
                                    PROJECT_ID         ,
                                    PROJECT_NAME       ,
                                    DIRECT_BOOKING     ,
                                    NON_ORACLE_PROJECT ,
                                    ATTRIBUTE1         ,
                                    ATTRIBUTE2         ,
                                    ATTRIBUTE3         ,
                                    ATTRIBUTE4         ,
                                    ATTRIBUTE5         ,
                                    LAST_UPDATE_DATE   ,
                                    DELETE_FLAG        ,
                                    CREATION_DATE      ,
                                    CREATED_BY         ,
                                    LAST_UPDATE_LOGIN  
                                    )
select HISTSEQ_NO_sq.nextVal,/*HISTSEQ_NO        */ 
       sysdate              ,/*HIST_DATE         */
       MKEY                 ,/*MKEY              */
       PROJECT_ID           ,/*PROJECT_ID        */
       PROJECT_NAME         ,/*PROJECT_NAME      */
       DIRECT_BOOKING       ,/*DIRECT_BOOKING    */
       NON_ORACLE_PROJECT   ,/*NON_ORACLE_PROJECT*/
       ATTRIBUTE1           ,/*ATTRIBUTE1        */
       ATTRIBUTE2           ,/*ATTRIBUTE2        */
       ATTRIBUTE3           ,/*ATTRIBUTE3        */
       ATTRIBUTE4           ,/*ATTRIBUTE4        */
       ATTRIBUTE5           ,/*ATTRIBUTE5        */
       LAST_UPDATE_DATE     ,/*LAST_UPDATE_DATE  */
       DELETE_FLAG          ,/*DELETE_FLAG       */
       CREATION_DATE        ,/*CREATION_DATE     */
       CREATED_BY           ,/*CREATED_BY        */
       LAST_UPDATE_LOGIN     /*LAST_UPDATE_LOGIN */
FROM xxacl_pn_project_link l
 WHERE l.mkey = '1'
To handle your HISTSEQ_NO field, giving that it has no autoincrement logic, you can use a sequence:
create sequence HISTSEQ_NO_sq start with 1