Can I store a LOOKUP field from a form in a different form?

Can I store a LOOKUP field from a form in a different form?

I have 2 forms/tables
One form has Facilty Name,  Address etc and the other form has  Client Name, DOB, address etc.
I want to be able to use the Facilty Name in form 1 as a lookup to populate form 2 and store it in a field named FaciltyKey.
The 1st form only has 1 record per facilty and  therefore it is the Master.
The 2nd form can have many records for each facilty so it should be the child ( a one to many relationship)
How do I store the value of the Loookup fiield in to the 2nd form?