You're likely currently using the https://api.mainnet-beta.solana.com
which is a publicly-available and free-of-charge RPC server that gives users a route to the Solana mainnet cluster network. This however has the downside of being congested and slow, hence the 403 error.
Private services (such as Quicknode) offer access to their own RPC servers (which are usually much more reliable) through a paid service. To use their servers instead you'll have to create an account with them. Here's a link to get started with quicknode. They also have free plans, but there isn't much difference between those and the default one you're currently using.
When you do create an account, they'll give you a link which you can run your transactions by. If you're using solana-cli, you can run solana config set --url <Whatever rpc url quicknode gives you>
. If you're deploying any other way, there should be an option somewhere to edit the url transactions are being sent against.
Good luck!