Can't tell you what you may have done as I am not 100% sure what you mean in your question.
Assuming your text layer is now your white layer - alpha to select to give a selection around the letters then bring your transparent layer to the top and the selection should show through. Then while the selection and layer is active fill it with the desired colour, pattern or do anything else you wish.
Note* you may have to fill it with a colour before doing certain modifications to it.
If your text layer is the transparent layer just move it to the top.
Assuming your text layer is now your white layer - alpha to select to give a selection around the letters then bring your transparent layer to the top and the selection should show through. Then while the selection and layer is active fill it with the desired colour, pattern or do anything else you wish.
Note* you may have to fill it with a colour before doing certain modifications to it.
If your text layer is the transparent layer just move it to the top.
