Hi,
First you have to create a many2one field with related model as Users(res.users).
After creating the field a compute function can given to the field in order to compute the current user. For that you can click on the ‘More’ button at the left bottom corner and will be redirected to the field properties. There under the ‘Advanced Properties’ section we can give the required dependencies and the compute function in python code as:

for record in self:
record ['x_studio_many2one_field'] = record.env.user

Now the field will compute the current user as its value.

Hope it helps