You can purchase inbound liquidity. You pay a lightning invoice and someone opens a channel with you. 
The fees are always changing and differ for different LSPs however an example would be something like you might pay an invoice of 10k sats to a LSP and then they will open a 1million sat channel with you. The 10k data covers the on-chain fee plus a fee to the LSP.
At first all the liquidity will be on their side so you will only be able to recieve transactions through this channel. But once you have received you will be able to send back out through that channel. 

 So how do?  

 Depends on how your node is set up. With Alby Hub this is integrated easily under the node management page. You can also purchase directly from the LSP if you don't have something like Alby's build in integration. You could take a look at the liquidity provider "lnserver". They have tutorials walking you through the process on different node setups.

https://lnserver.com/ 

 Also I have just had a look and on chain transaction fees are quite high right now so that may make it expensive. It's better to open channels when the fees are low. 

 I appreciate it. I'm using core-lightning at the moment and the cli tool 

 I have no experience with this personally. Hopefully the lnserver tutorials give you enough insight to get this to work for you.