Look into Accounts & Privileges.
You can look into 2 methods depending on your needs...
1. Users have access to what is applicable to their group.
2. Users have access to only their records.
Sounds like you are after #2.
Add a field to each table you want to restrict access to, call it Owner.
Have an auto enter on creation formula to insert Get (AccountName) into this field.
Go into Accounts and Privileges and setup user accounts, create a Privilege Set for these users also.
Edit the Privilege Set, Data Access and Design, Records... Select Custom privileges...
Select the table, at Set Privileges do the following on View and Edit and Delete actions:
Select Limited and enter the following formula:
Owner = Get (AccountName)
Note Owner is the field that is auto updated to the logged in user account name.
What this will do is restrict record access to only the user whose account name is in the owner field.
You may find when looking at layouts users see <No Access> in the field, just do a find on either owner = get(accountname) or, just a find with wildcard such as * on any field, this will restrict the found set to the records the user has view privileges for.