you have to contact an attorney. They will start the process. We did it for a relative in 2015 in Georgia and the cost was about $6000 total. This is paid out of your loved ones funds if he/she has the money.
There are multiple steps I cannot even remember the details. A lawyer will step you through it.
You need a Lawyer. You have to prove someone is no longer competent to make informed decisions for themselves. This will mean at least a couple of doctors saying this is so after a battery of testing. Then you go before a judge with the one you are seeking guardianship present, usually. There could also be people there contesting your guardianship. A Judge will rule if you get guardianship. If you do, you will be responsible for keeping records for the States yearly review. This all is very expensive.
There are multiple steps I cannot even remember the details. A lawyer will step you through it.
So, in general, it depends on each state. I suggest you contact an attorney in the state of the potential Ward's residence.
You can also check out the state web site of the state in which the potential Ward lives for more details.