Hi @Nana5.
A warm welcome here at the Roku Community!
Thanks for reaching us here regarding this matter. No worries, we'd be more than happy to assist you with this.
Whenever your keyboard pops up, press the arrow up ↑ before pressing the letter that you wanted to be capitalized.
If you need further clarification and assistance, let us know! Thanks.
All the best,
Carly
Carly Y.
Roku Community Moderator