Bridges. Mainnets. Matic?

Okay bare with me! So me and the bf have been buying NFTs. We bought Eth and bridged it to weth. Not a problem but each time we do this it's costing us a fortune in gas fees. Is there a cheaper easier way to bridge?

We know you can swap it on sites like sushi but don't understand how to get the matic onto our Polygon mainnet instead of the Ethereum mainnet 🤦🏻‍♀️😭

Any help will be rewarded! I'm desperate!!!! 😭