Hi @aliciap63716589 ,
While I have not used Textile Designer, I saw a demo once, and they seemed to have borrowed it straight out of Illustrator. You will most likely need to recreate the pattern in Illustrator, so it should be easy to figure out once you get started.
By default, patterns are stored in the Swatches panel of the file you are working in. Here are some tutorials to get you started.
https://helpx.adobe.com/illustrator/how-to/create-apply-patterns.html
https://design.tutsplus.com/articles/a-beginners-guide-to-adobe-illustrator-patterns--cms-33351
If you need more help, then show a screen shot. Is it okay to move this to the Illustrator forum?
~ Jane