Dear Carmen, if you are confident in the meaning of your two scales but need to perform a reliability analysis, have a look at my guide to reliability analysis. 20 items is a bit high though so you may find that your scales break down into several sub scales. This may take you into exploratory factor analysis. Again there is a guide on my page.
Are you asking about how to import your data into SPSS? If so, try this: Open SPSS, then File - Open - Open Data. Select the type of file your data is currently in in the 'Files of Type' drop-down menu, then follow the steps in the dialogue boxes. This is a useful online guide: https://help.fresnostate.edu/facstaff/software/spss/importdatabase.php
The simplest approach would be to enter the data into SPSS in the first place. If you've already got the data in some other format, then try what Louise suggested or just try to open the file directly from SPSS. Another approach (one I've often used) is to copy-and-paste the data from, say, an Excel spreadsheet into SPSS. This works fine. The only thing is, you need to set up the variables in SPSS (i.e., name them and determine their nature). This can be done after the copy-and-paste operation except for string variables (such as ID codes). But really: it's pretty easy. Hope your data are interesting!