How do I give advice to someone...

1. I don't know if you can really motivate them yet, because from what I'm hearing they may be having a depressive episode or have depression. I would say that you should offer to help, and not vaguely. Instead of saying "Do you need anything?" , say that you'll get groceries for them or do laundry. Stuff like that becomes really difficult when you have depression and would be a big help when they can't get out of bed or struggle with wanting to go outside.

2. Come by a lot. Invite over or go over. Maybe don't invite them out (might be outside comfort zone) but just make sure they're doing okay and have attention. Depression makes you lonely, and they probably need a good laugh at times, even if it doesn't fix the situation entirely. It's also a precautionary measure, in case they may do something to hurt themselves.

3. If depression is getting in the way of their daily life, recommend a doctor. Even if they are opposed to it, do it anyway. If your friend has not yet seen a doctor, encourage them to seek help and reassure them that there is nothing wrong with asking for assistance. Depression is a real—and treatable—illness. If your friend is already seeing a doctor, offer to help with picking up medications and being on time for appointments.

4. Advice isn't the most important part, participating in their recovery and being there should be your first priority if you want to help them.

You can always pm if you want any specific situational advice.