When using TA to attend college, how do I only take out the loans I need, and not the full amount?

Depending on your institutions website, you can increase or decrease the amount on your own. They will show you your max amount given for the semester lets say $5000 but you can change the amount to $2000. If you go to your school's version of a student portal under financial assistance or some other title, it should be there. If you take less but need more, you can always increase it later in the semester.

With TA, you have to send your TA voucher or award letter, dont remember the exact name of the document right now, to your school certifying official or financial aid office. It lets the school know that the military will be paying a portion of your bill. The school will then send the army an invoice and dont forget to send in your grades after the semester is over otherwise the military might not pay it and you will be stuck with the balance.

Are you asking about Tuition Assistance? That's not a loan...and if you're getting a Bachelor's you shouldn't need to take out any loans using TA. If you're in graduate program, you will have to pay about half after TA.

I came in with a Bachelor's so I used TA for my first Master's. For about half the time I could afford to pay the part that TA didn't cover. Then life happened - and for the last 3 months of that degree I used my 9/11 GI Bill and TA to pay for it.

For my second Master's, I used my 9/11 GI Bill on that one.

You need to be going through the Veteran's assistance office at the college you're applying to so that everything gets annotated properly. But I'm not sure why you'd need any loans using TA for a Bachelor's. It should cover all of it.