Introduction to SPSS

First, Click "Transform" under the toolbar, then choose either "Recode into Same Variables..." or "Recode into Different Variables...". A window would be shown below:

Choose the variable name you would like to recode, click the switch button and let it into "Variables".

Then click the "Old and New Values" button, a window would be shown below,

Setting a numeric value for each level of the categorical variable, then "Add" it each,

After modifying each level of this variable, click "Continue" and "Ok" to finish converting. Then, all string type levels of this variable would automatically be converting to the numeric value.

Second, switch from the Data View Page to Variable View Page.

Noticed that each variable type would be shown under the "Type" column. Click the small button variable type right beside the "String", change it from String to Continuous.

The next step is recording the variable. Noticed that a string type variable would show "None" under the "Values" column.

 

Click the small button right beside the "None", a window would be shown as the following,

Setting a value for each level, then click the "Add" button to recode them,

Once you recode all levels for each categorical variable, click the "OK" button.

Next, Change this variable type from "Categorical" to "Ordinal".

Finally, switch back to the Data View Page. A  "Value Label" button under the toolbar would check if you correctly and completely setting each level's value.

Clicking this button, you could review the label for each level.