TAG is a subscription link, not an app to install. Here's exactly how to add it to the client you already use.
After choosing a plan, you'll receive a personal subscription URL. Copy it — this single link is everything your client needs.
If you don't already have one, install Clash Verge or Mihomo Party (desktop), v2rayNG (Android), Shadowrocket (iOS) or sing-box. These are independent, widely used third-party clients — not TAG's own app.
Open the client's subscription or profile settings, paste the URL, and save. The node list populates automatically from your TAG subscription.
Pick a node from the imported list — or leave the client on auto-select — and turn the proxy on from within the client's own interface.

Clash Verge, Mihomo Party, v2rayNG, Shadowrocket and sing-box are mature, independently maintained clients with their own update cycles, routing rules and interfaces. Building a TAG-branded app on top of that would mean maintaining a worse version of tools that already work well.
Instead, TAG focuses on the part that's actually ours to get right: the subscription link, the node pool behind it, and documentation that keeps up with how these clients actually behave.
If a step above doesn't match what you're seeing in your specific client version, the Contact page is the fastest way to reach us for that particular setup question.
Your subscription link is issued after you choose a plan on the Pricing page. It's personal to your subscription — don't share it publicly.
Double-check the link was copied in full with no line breaks, and that your client is updated to a recent version. If the issue continues, reach out via Contact with your client name and version.
That depends on your plan's device allowance — see the Pricing page for how tiers differ on simultaneous device use.