Taking Course at Different University

[polly181920]

Hello! I am going to be taking stats through Athabasca University. However, when I go to add in the prerequisite through ORPAS, my home university is greyed out, and I am unable to indicate that I am taking this course through another institution. Has anyone run into this and if so, how do I work around it? I don't want my application to be messed up because of this, as I do have all the pre-reqs. Also, does anyone have any advice for LOI? Feeling a bit overwhelmed with squeezing everything in while keeping it succinct and maintaining a flow. 

Thanks so much and good luck everyone!