Search for text help please

Hello everyone.

I have a column with thousands of entries,  with text entries. I want to be able to search for ones that begin with L1.

I'll have entries likes this xxxxxxxxxxxxxxxxxxxx and some like this L1 xxxxxxxxxxxxxxxxxx.

How would I search for just the L1 ones please? I'd like it to be a new column in the table called L1

Thank you for any help, its much appriecated