You can assign specific offers to your guides by adding the guides as multi-users to your user account. You can find this feature under Settings > Multi-User.
First, select the users to whom you want to assign specific tours. Click on the Pen to edit the users.
Note: You can find out how to create a multi-user in the following article: How can I create a multi-user?
Under Grant this user access to > User actions check Calendar > Only assigned availabilities.
Save the newly created multi-users and go to the menu item Calendar in the account.
Now select the desired offer by clicking on the tile. A white window will open in which you can select the multi-users previously created under Assignee.
Now select the desired offer by clicking on the tile. A white window will open in which you can select the multi-users previously created under Assignee.
After the assignment, your guides (multi-users) now have access to the offer in the calendar that you have assigned to it.
Note: In this context, check whether the function of assigning a booking to a user is in your interest: How do I assign bookings to multi-users?