An EVM compatible wallet like Metamask is required to interact with most ethereum based exchanges.
If you haven’t downloaded and set up your Metamask, you can download it first.
Ethereum mainnet is automatically added to your Metamask configuration by default.
You can send Ethereum from your favourite exchanges such as Binance or Kucoin by withdrawing your ETH to your Metamask wallet address as shown below
Visit the official Uniswap Website, please make sure to look at the URL as there are phishing sites that are similar to the official website.
Once you are on the website, click the "Connect Wallet" button on the top right corner and select Meta Mask.
Make sure to change the network on your Meta Mask to the Ethereum Mainnet as well ( Meta Mask should prompt you )
Click on the "Select a Token" dropdown and find the token you want to swap for.
You can then swap your ETH for OTHR in the Swap page as shown below. ( Keep some ETH for gas fees )
Do remember to set the slippage tolerance accordingly if there is any buy and sell tax involved or if liquidity is low.
If you can't find OTHR in the swap, you can manually import it using the contract address.