To perform a cross join (often between the dimension), you have two ways :
To know what sort of join is is a cross join, follow this link : SQL - Cross Join / Cartesian Product / Cross Product
As the cross join is mainly used to densify the data, you can find the design details in this paragraph from this article.
In an answers advanced tab, you can set directly a Sql statement.
Example of cross join with Obiee logical sql :
SELECT C.saw_0 saw_0, B.saw_0 saw_1, B.saw_1 saw_2 FROM
( Select Calendar."Calendar Year" saw_0, Fiscal."Fiscal Week Number" saw_1 FROM SH ) B,
( Select Products."Prod Name" saw_0 FROM SH ) C