I saw this post and another of yours and thought that you might not be aware of the C3 manual. It is really well organised and searchable and contains all the information for these basic questions. Have a read, it is really helpful.
In answer to what I think your specific question is, when you create the variable you need to set its type to "string". This variable can store text strings. Number variables can only store valid numbers.
Otherwise if you are just looking how to store a value in a variable please have a look at the manual entries.