How to shift signal phase in matlab from this circuit?
The reason there are "red dot's" is because you are attempting to cross domains.

Simulink contains multiple physical domains which prior to Simscape was not that obvious (in simscape electrial, mechanical, magnetic, hydraulic, etc.. all have unique trace colours). 

In the example shot above you are attempting to connect BASE Simulink to SimPowerSystems (Specialist Technology, not Simscape electrical). These are completely incompatible and you would need to use  "Controlled Voltage Source" to produce a time varying SimPowerSystem voltage that could be fed into a passive array to create a phase shift and an attenuation.

If you are just after a phaseshift may I recommend using a Transport Delay block (Simulink -> Continuous) 

If however you are after a more electrical affect then a suitable transfer function \$\frac{1}{1+\tau s}\$ would produce an equivalent electrical response while residing within the S-domain/Simulink 

Or convert the model to SimScape/SimPowerSystem and model based upon "real" R's and C's